Thermodynamic study of aqueous 2-(isopropylamino)ethanol. A sterically hindered new amine absorbent for CO₂ capture

Highlights: • Density and ultrasound speeds were measured in 38 aqueous mixtures of 2-(isopropylamino)ethanol. • Excess molar and limiting molar and partial molar properties were derived and interpreted. • Temperature and composition derivatives of different order give relevant hydration and molecular aggregation information. • A quantitative measure of the screening effect to the H-bonding ability of the amine group is proposed. - Abstract: Simultaneous measurements of density and sound speed, at five temperatures, T = (283.15 to 303.15) K and over the whole composition range were performed in 38 aqueous mixtures of 2-(isopropylamino)ethanol (IPAE), a sterically hindered amine of new generation with potential use in CO₂ capture. Composition and temperature effects on different molar, excess molar, apparent molar and partial molar properties such as volume, isobaric expansion and isentropic compression are analysed, in order to assess different changes in the hydration and association patterns, across the entire composition range. A quantitative measure of the screening effect produced by the bulky hydrophobic part of IPAE to the H-bonding ability of the –NH group to the water molecules, is proposed. A comparison of the different thermodynamic properties, derived for this system, with those for the aqueous system of 2-(ethylamino)ethanol (EEA), is made. This last compound has a common structural –NHCH₂CH₂OH group sequence and a smaller and linear hydrophobic part