Solvatochromic Parameters of Four Amines in Propane-1,3-diol at 298.15 K

One of the most used methods for capturing acidic gases from the atmosphere is the use of amines that react with the acids and can later be recovered. The choice of amines that are most efficient in capturing has been the subject of several studies; however, the energy effort for their regeneration is also important. While the polarity of the solvent plays a critical role in determining which amines efficiently capture CO₂, the heat capacity of the solvent is also a significant factor in the regeneration process. In this work, we present values for Reichardt's ETN30 and Kamlet-Taft parameters, such as <i>π</i>* (dipolarity/polarizability), <i>α</i> (acidity), and <i>β</i> (basicity), for solutions of two alkanolamines and two alkoxyamines dissolved in propane-1,3-diol, at 298.15 K, a solvent with a lower heat capacity than water. In addition to the polarity characterization of the amines in that solvent, the aim of this study is to analyze the differences observed in the solvatochromic parameters when water is replaced by alcohol. The impact of this change on the values of those parameters for the binary amine + solvent solutions was assessed by calculating the transfer values, ΔtransfFi,xi. Defined as, ΔtransfFi,xi=Fi1,3PD-FiH2O, these transfer values represent the difference in the parameters when the amines are transferred from water to alcohol. While the water medium is more favourable in terms of <i>π</i>* for CO₂ capture, the alcohol medium appears to hold more promise in terms of <i>β</i>.