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Thediamine 3-（methylamino）-propylamine （MAPA） and eight tertiaryamines were studied as single and blended aqueous CO2 absorbentsat different concentrations and ratios to investigate their reactionmechanisms. After absorption （40 °C） and desorption （80 °C）experiments, quantitative 13C NMR experiments were performedon each liquid sample. After absorption, the following CO2-derived species were identified and quantified: （bi）-carbonate ineach amine system, primary and secondary MAPA carbamate and MAPA dicarbamatein MAPA systems, and tertiary amine carbonate in tertiary amine systems.Concerning desorption, the main CO2 species removed was（bi）-carbonate, followed in the blends by MAPA dicarbamate. Since,after CO2 absorption, the concentration of MAPA dicarbamatewas negligible in single MAPA and, in the blends, mainly increasedat increasing pKa of the tertiary amines,it is concluded that the tertiary amines increase the availabilityof MAPA species to react further with CO2. MAPA and tertiaryamines appear to influence each other also for the CO2 release.
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