Abstract: Monoethanolamine (MEA) and mono-n-propanolamine (MPA) molecules were investigated for CO2 binding using Density Functional Theory. MPA was predicted to bind CO2 better than MEA along the bimolecular and trimolecular pathways. The additional CH2 in MPA provided additional polarization to reduce the electrostatic repulsion for the charge-separated zwitterionic intermediates (ZW) as shown in the Polarizable Continuum Model calculations; also became more polar solvent to stabilize ZW. 25% and 50% CO2 loading at 400 K were studied by first-principle molecular dynamic simulations. With including the explicit solvation effect, CO2 in alcoholamines favored a reduced-hydrogen-bonding (HB) environment. The probability of identifying the HB precursors-(MEA)2 and (MPA)2 for the subsequent trimolecular pathway decreased. Moreover, higher CO2 uptake accompanied with more OH⋯N HB, and the lone pairs of N were blocked to CO2. Water also preferred to form intermolecular OH⋯N HB so that the accesses of CO2 were hindered.
ASJC Scopus subject areas
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry