Computational study of thermodynamics of polyamines with regard to CO₂ capture

A computational study has been performed on predicting pKa values for polyamines, these having a potential for being used as solvents in CO₂ capture processes. In this article, we have coupled density functional theory with continuum solvent models (PCM and SM8T) to calculate the aqueous pKa of polyamines. No empirical correction terms were employed in the calculations except for the free energy of solvation of the proton (H+) in gaseous phase and in aqueous phase. The B3LYP functional and 6-311++G (d, p) basis set were used in all the calculations. Gas phase conformer search at HF/3-21G*level was carried out. As, post combustion CO₂ capture is a temperature swing process, senstivity of pKa values of polyamines with temperature is an important variable.