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Aqueous MAPA, DEEA, and Their Blend as CO2 Absorbents: Interrelationship between NMR Speciation, pH, and Heat of Absorption Data
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Onthe basis of speciation by nuclear magnetic resonance （NMR）spectroscopy, heat of absorption, and pH data, the reactions occurringin aqueous MAPA （3-（methylamino）-propylamine）, DEEA （2-（diethylamino）-ethanol）,and their blend at various carbon dioxide （CO2） loadingswere identified and discussed. At increasing CO2 loading,the basicity of the solutions decreased. In the MAPA solvent, thisled to the hydrolysis of the carbamate species, which correspondedto a drop in the heat of absorption. In the blend, due to the activityof DEEA, such a drop in both pH and heat of absorption was not noticeable.In the presence of MAPA, in the early loadings DEEA had not yet aninfluence on the （bi）-carbonate formation but mainly on the MAPA activity.However, as soon as the trend for （bi）-carbonate formation went asin DEEA singly, the released heat steadily decreased. Both in singleand in blended MAPA, the carbamate hydrolyses started at similar pHvalues, i.e., about 9.8–9.5.
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