Reversible carbon dioxide capture by aqueous and non-aqueous amine-based absorbents: A comparative analysis carried out by 13C NMR spectroscopy

The efficiency of CO2 uptake by the amines 2-(2-aminoethoxy)ethanol (DGA), 2-amino-2-methyl-1,3-propanediol (AMPD), 2-amino-2-methyl-1-propanol (AMP), 2,2′-iminodiethanol (DEA) and 2-(butylamino)ethanol (BUMEA) has been investigated either in aqueous and in 2-(2-methoxyethoxy)ethanol (DEGMME) solutions and compared with 30% aqueous 2-aminoethanol (MEA). Batch experiments were carried out to measure the CO2 loading capacity of the different amine solutions and the rate of CO2 absorption. The 13C analysis has been applied to identify and quantify the carbonated species in solution upon CO2 uptake. The efficiency of CO2 (15% in air) capture was measured in continuous cycles of absorption (40 °C) and desorption (110 °C) carried out in packed columns at room pressure. The efficiency of the aqueous absorbents is greater than 90% and overcomes that in 2-(2-methoxyethoxy)ethanol. The CO2 absorption heat of aqueous BUMEA and DGA in DEGMME calculated using Gibbs–Helmholtz equation was found to be lower than that of conventional 30% aqueous MEA: the possible advantages of these systems with respect to aqueous MEA as CO2 absorbents have been discussed.