Physicochemical Properties of the System N,N-Dimethyl-dipropylene-diamino-triacetonediamine (EvA34), Water, and Carbon Dioxide for Reactive Absorption

Abstract

Aqueous solutions of N,N-dimethyl-dipropylene-diamino-triacetonediamine (EvA34) are promising solvents for CO 2 capture. Therefore, in the present work, a comprehensive experimental study was carried out to determine data on physico-chemical properties of EvA34 and its mixtures with H 2 O and CO 2 . The liquid density and the dynamic viscosity was studied for pure EvA34, as well as for unloaded and CO 2 -loaded 1 aqueous solutions of EvA34. The liquid heat capacity was studied for pure EvA34 and unloaded aqueous solutions of EvA34. Furthermore, data on the vapor pressure of pure EvA34 was recorded. The pH-value was measured for unloaded and CO 2 -loaded aqueous solutions of EvA34 and the dissociation constants of EvA34 were determined from titration curves. Moreover, data on the solubility of CO 2 in aqueous solutions of EvA34 and data on the CO 2 -containing species in the liquid phase of these solutions were recorded. Most of the new data was taken at temperatures between 293 and 393 K. The mass fraction of EvA34 in the unloaded aqueous solutions was eitherw 0 EvA34 = 0.1 g/g orw 0 EvA34 = 0.4 g/g. The CO 2 -loading was up toα CO 2 = 6.2 mol/mol. The new data were compared to corresponding data of two standard amines that are used for CO 2 capture: monoethanolamine (MEA) and a blend of methyl-diethanolamine and piperazine (MDEA/PZ). The comparison revealed that EvA34 combines favorable properties of MEA and MDEA/PZ in one molecule.

Triacetoneamine-derivates (EvAs) for CO2-absorption from process gases

“…Results for aqueous solutions of EvA34 from head space gas chromatography experiments of this work were compared to a corresponding data set from a previous work of our group with the same apparatus [57]. The results are in good agreement.…”

“…The highest pK-value was assigned to the α-N-atom for all EvAs. Literature data [26,57,60] and the positive inductive effect of the surrounding 2,2,6,6-tetramethyl-piperidinering support this assignment. The second highest pK-value was assigned to the N-atom that has the highest spatial distance to the α-N-atom.…”

“…The molal activity-based pK-values of highly diluted aqueous solutions of EvAs were determined by titration experiments at 20 , 40 , and 60 . The equipment and the way the experiments were conducted and evaluated were the same as in a previous work of our group [57]. Therefore, no details are given here.…”

“…The standard uncertainty of the measured pK-value is calculated from the standard deviation of repeated experiments of previous works of our group [26,57] and from the standard uncertainty of the calibration and is u(pK) = 0.15 on the pH-scale. The expanded uncertainty of the temperature measurement is U (t) = 1 (0.99 level of confidence).…”

“…The CO 2 -solubility in aqueous solutions of EvAs with a mass fraction of EvA in the unloaded solvent ofw 0 EvA = 0.4 g/g was measured by head space gas chromatography at 40 and 100 . The equipment was the same as in previous works of our group [57,58,59] and is therefore not described here in detail. For the screening, the samples were prepared in stainless steel cells that were directly used in the head space gas chromatography apparatus.…”