Thermodynamic Study of a Complex System for Carbon Capture: Butyltriacetonediamine + Water + Carbon Dioxide.

Different thermodynamic properties of aqueous solutions of butyltriacetonediamine (BuTAD), unloaded and loaded with carbon dioxide, are studied experimentally. For unloaded mixtures of BuTAD and water, protonation equilibrium constants between 283 and 333 K and liquid-liquid equilibria between 313 and 353 K, including the lower critical point, are determined at atmospheric pressure. Furthermore, the solubility of carbon dioxide in aqueous solutions of BuTAD between 313 and 393 K is determined at low loadings with an analytic method based on headspace gas chromatography and at high loadings with a synthetic method using a high pressure view cell. In the loaded system, solid precipitation, liquid-liquid phase split, and the presence of metastable states are observed in certain ranges. The data is interesting for assessing the aqueous solution of BuTAD as solvent for carbon capture. A short-cut method is used for comparing the new solvent with an aqueous solution of monoethanolamine (MEA) with respect to the energy requirement of an absorption/desorption process for CO2 scrubbing. Furthermore, a new and simple gas chromatographic method for determining the loading with carbon dioxide of aqueous solutions of amines is described. [ABSTRACT FROM AUTHOR]