Structure and dynamics of CO2 absorption in aqueous potassium lysinate solutions

Abstract

Aqueous amino acid salt (AAS) solutions are promising alternatives to conventional alkanolamines for CO2 capture. In this work, we employ molecular dynamics simulations using a solvation and slab model to examine structure and dynamics of CO2 absorption in aqueous LysK (potassium lysinate) solutions. The simulations focus on system density, inter-molecular interactions characterized from Radial Distribution Functions (RDFs), diffusion coefficients (D) and interfacial versus bulk absorption at varying temperature, water and CO2 concentrations. The results from solvation model show that Lys−–CO2 interactions increase as the aqueous LysK concentration, temperature and CO2/LysK molar ratios decrease. CO2 molecules interact favorably with the N1 site of the lysinate anion while CO2-water interactions too play a competing role with N1-CO2 interactions. DCO2 decreases with increase in aqueous LysK concentrations for all temperatures and CO2/LysK molar ratios. The molar absorption of CO2 decreases with an increase in the concentration of aqueous LysK solution. An increase in CO2 partial pressure in slab models and decrease in the concentration of aq. LysK solution leads to a higher molar ratio of CO2 absorption.