On the CO₂ Capture in Water-Free Monoethanolamine Solution: An ab Initio Molecular Dynamics Study

Abstract

Monoethanolamine (MEA) based liquids are widely used materials for postcombustion CO2 capture. We report here an extensive ab initio molecular dynamic (AIMD) simulation study on CO2 sorption in water-free MEA liquid with a range of CO2 contents at 313 K. The simulation reveals the detailed CO2 capture mechanism that leads to the initial formation of a zwitterion species and the ultimate proton transfer from the zwitterion to a nearby MEA molecule. The ion pairs formed in the liquid result in strong electrostatic interactions among the molecules in the liquid. The variation of liquid density, volume, diffusion coefficient, power spectrum, and average heat of sorption at the selected CO2 loadings was systematically assessed. The results indicate that initially the volume of the MEA solution expands gradually and tops at 60% of CO2 loading. After that, the volume declines as a result of strong Coulomb interactions among the ion pairs at higher CO2 loadings. The calculated liquid densities and the average heats of sorption are in quantitative agreement with the available experimental values. The simulated power spectrum of the water-free liquid also resembles the infrared spectrum of 30% aqueous MEA solution. The characteristic features in the simulated power spectra are slightly blue-shifted upon CO2 uptake.

Kinetics of CO2 absorption by aqueous 3‐(methylamino)propylamine solutions: Experimental results and modeling

“…To understand the mechanism of CO 2 absorption into aqueous MAPA solutions, fundamental knowledge of the liquid structure, not obtainable from macroscopic kinetic studies, is needed. Molecular modeling studies on the CO 2 absorption in aqueous MEA solutions are available in literature . Because studies with different modeling premises may come to different conclusions regarding the stability of conformers, caution should be taken when evaluating the results.…”

Solvation Dynamics of CO2(g) by Monoethanolamine at the Gas–Liquid Interface: A Molecular Mechanics Approach

“…However, because of the use of ethylene oxide as the starting material for synthesizing alcoholamines, the hydroxyl groups are inherently present in CO 2 scrubbers. Compared with the CO 2 -binding characteristic of the amino groups, the hydroxyl groups can shuttle protons from the quaternary nitrogen of the ZW intermediates to the CO 2 − moieties, as shown by ab initio molecular dynamic simulations of CO 2 in neat MEA liquid [ 20 ]. However, this proton transfer capability of the hydroxyl groups is anticipated to be less effective compared with that of water molecules.…”

The thiocyanate anion is a primary driver of carbon dioxide capture by ionic liquids

“…This stage also includes separation of carbon dioxide from other omnipresent gases, such as nitrogen, oxygen, water vapor, noble gases, etc. [16][17][18] Despite being definitely useful and widely applied, CCS is not cost efficient. Regeneration of adsorbent after CO 2 removal requires large amounts of energy.…”