Understanding the CO2 capture performance by MDEA-based deep eutectics solvents with excellent cyclic capacity

Abstract

Solvents for CO2 capture with efficient regeneration are essential for industrial applications. Here, three methyldiethanolamine (MDEA) based deep eutectic solvents (DESs) were developed and their performance for CO2 uptake and regeneration was evaluated. Density functional theory (DFT) calculation and molecular dynamics (MD) simulations were performed to elucidate the features of DES and the DES interaction with CO2. The CO2 absorption performance is dependent on the hydrogen bond acceptor (HBA). [Monoethanolamine hydrochloride (MEAHCl)][MDEA] exhibits the best CO2 absorption performance, which is further enhanced by the addition of monoethanolamine (MEA), reaching 13.5 wt% after 6 h of absorption at 25 °C when the ratio of MEAHCl, MDEA, and MEA at 1:3:0.5. Both DFT calculation and MD simulations reveal that the CO2 interaction with [MEAHCl][MDEA] is via the –NH2 group in MEAH+ and the –OH group in MDEA, also confirmed by nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FTIR) results. The ternary DES of [MEAHCl][MDEA][MEA] with low desorption activation energy exhibits excellent cyclic capacity after 5 cycles of regeneration, offering an efficient and low-cost CO2 capture system for industrial applications.