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. D_CO2 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.