Solubilizer reconstructs the influences of the hydrogen-bond network of nonaqueous biphasic solvent on the absorption, phase splitting and desorption

Abstract

Nonaqueous biphasic solvent has remarkable energy-saving potential. The weak force between N, N, N′, N″, N‴-pentamethyldiethylenetriamine (PMDETA) and Dimethyl sulfoxide (DMSO) contributes to facilitating the separation between DMSO and PMDETA, thereby enabling efficient liquid–liquid phase separation. Nevertheless, the weak interactions of PMDETA with other solvent molecules pose considerable challenges in the formulation of fresh homogeneous phase solutions. This study proposes a strategy to enhance PMDETA dissolution by introducing a solubilizer into a hybrid phase splitter, thereby increasing the concentration of PMDETA in the solvent. With the addition of a small quantity of solubilizer, the absorption, regeneration, and phase separation performance among the absorbents are comparable. The phase separation performance is influenced by the number of hydrogen bonds formed by the solubilizer, and the concentration of solubilizer in the lower phase is dependent on its hydrophobicity. Characterization using 13C NMR and FT-IR indicates that CO2 products primarily exist in the form of MEACOO−/MEAH+. Through DFT and molecular dynamics simulations, the impact of the solvent environment surrounding Ethanolamine (MEA) on the MEA+COO− deprotonation reaction is analyzed. While PMDETA offers a more favorable proton acceptance energy compared to MEA, the limited opportunities for PMDETA to come into contact with MEA molecules may be the primary hindrance to its participation in the reaction. Significantly lower corrosivity and regeneration energy requirements for non-aqueous biphasic solvents compared to 30 wt% MEA make them ideal candidates for energy-efficient, low-corrosivity CO2 capture.