Combined experimental and computational study on the effect of solvent structure on developing CO2 biphasic absorbents

Abstract

To explore the regulatory factor of phase separation and the effect of solvent structure, the phase separation behavior, absorption/desorption performance, viscosity change, heat duty and ternary phase diagram of 3 monoethanolamine(MEA)-based phasic absorbents using 3 alcohols with various carbon chain lengths and isomers were determined by comprehensive experiments. The tunable phase separation behavior of MEA-based biphasic absorbents can be achieved by adjusting the mass concentration ratio of solvent and water, and the CO2 loading of phase separation point was much more impacted by the effect of the carbon chain length than that of isomerism. The intermolecular interactions between species in solutions before and after CO2 absorption were analyzed by the classical molecular dynamics simulations and independent gradient model analysis. Based on the experimental and computational results, the fundamental mechanism of phase separation was elucidated, which is related to the broken of hydrogen bonds between solvent with H2O or MEA, and the enhanced interaction among MEACOO−, MEAH+ and H2O. This study highlights the effect of structure effect on developing advanced CO2 biphasic absorbents, which may reduce the energy consumption of regeneration significantly.