Capturing CO2 using novel nonaqueous biphasic solvent TMEDA/MEA/DMSO: Absorption and phase splitting mechanism

In order to ameliorate the issues of corrosion and high regeneration energy associated with traditional biphasic solvents, a nonaqueous biphasic solvent has been proposed as a potential alternative. This study introduces Tetramethylethylenediamine (TMEDA) as a phase splitter within the Ethanolamine (MEA)/Dimethyl sulfoxide (DMSO) system, resulting in a novel nonaqueous biphasic solvent, TMEDA/MEA/DMSO. Compared with other screened phase splitters, the appropriate polar size and intermolecular interaction force of TMEDA are the key factors that make it comply with the screening of nonaqueous biphasic solvent. When the mass ratio of TMEDA/MEA/DMSO is maintained at 3:3:4, the CO2 loading attains 0.54 mol (CO2)/mol (MEA), with the rich phase comprising 75 % of the total. 13C NMR and FT-IR characteristics showed that the absorbent product is mainly in the form of MEACOO−/MEAH+. Absorption and phase separation mechanisms of absorbent elucidated by DFT calculations and molecular dynamics simulations. The limited opportunity for TMEDA to interact with MEA molecules emerges as the primary reason for its reduced involvement in the reaction, with the inclusion of TMEDA intensifying the aggregation of MEACOO−/MEAH+ and triggering phase transition. In comparison to a 30 wt% MEA water-based absorbent, TMEDA/MEA/DMSO exhibits a 40 % reduction in regeneration energy (estimate) and possesses energy-saving attributes, rendering it a promising candidate for CO2 capture.