1 research outputs found
Monoalkylcarbonate Formation in Methyldiethanolamine–H<sub>2</sub>O–CO<sub>2</sub>
In this work, the monoalkylcarbonate
((<i>N</i>-hydroxyethyl)Â(<i>N</i>-methyl)Â(2-aminoethyl)
hydrogen carbonate) formation in
the system methyldiethanolamine (MDEA)–water (H<sub>2</sub>O)–carbon dioxide (CO<sub>2</sub>) is investigated by nuclear
magnetic resonance (NMR) spectroscopy. Aqueous solutions containing
0.4 g/g of MDEA were loaded with CO<sub>2</sub> in valved NMR tubes,
and the composition of the liquid phase in equilibrium was determined <i>in situ</i> at 298 K at pressures up to 11 bar. By two-dimensional
NMR, the presence of monoalkylcarbonate was verified, which has been
widely overlooked in the literature so far. The experimental data
of this work and reevaluated NMR data obtained in previous work of
our group were used to calculate chemical equilibrium constants of
the proposed monoalkylcarbonate formation. A model taken from the
literature that describes the solubility of CO<sub>2</sub> in aqueous
solution of MDEA and the corresponding species distribution is extended
so that it can account for the monoalkylcarbonate in the liquid phase
as well. The extended model is validated using NMR data in the temperature
range 273–333 K. The study shows that more than 10 mol % of
the absorbed CO<sub>2</sub> is bound as monoalkylcarbonate under conditions
relevant for technical applications