Solvents for CO2 capture. Structure-activity relationships combined with vapour-liquid-equilibrium measurements

In this study a systematic approach was chosen to test and characterize amine systems for CO2 capture. Vapour-liquid-equilibrium measurements were performed on a homologue series of amines, with ethylene amine as base structure. Various functional groups were used that ranged in chemical and physical properties. The effect of the addition of the following functional groups was investigated: -NH2 (ethylene diamine), -COOH (β-alanine), -SH (cysteamine), SO3H (taurine) and -OH (monoethanolamine). Of these amine systems, MEA and taurine showed comparable behaviour in CO2 absorption and desorption. β-alanine formed relatively more (bi)carbonate. As expected, no direct correlation in absorption behaviour with pKa was found, whereas there was a linear correlation between desorption behaviour at a fixed partial pressure with pKa.