Understanding the potential benefits of blended ternary amine systems for CO2 capture processes through 13C NMR speciation study and energy cost analysis

Aqueous blends of the three amines 2-aminoethanol (MEA), N-methyldiethanolamine (MDEA) and 2-amino-2-methyl-1-propanol (AMP) were tested as sorbents for CO2 capture processes. We formulated three different blends with the same overall amine concentration (5M) but with different amine molar ratio, namely blend-1 (2M MEA+2M MDEA+1M AMP), blend-2 (1M MEA+2M MDEA+2M AMP) and blend-3 (2M MEA+1M MDEA+2M AMP). Their CO2 absorption and desorption performances were investigated in batch experiments in terms of CO2 equilibrium solubility, CO2 absorption at 40 °C and CO2 desorption at 100 °C as a function of time, and energy consumption during the regeneration process. The results were compared to those obtained under the same operating conditions with 5M aqueous MEA, the benchmark sorbent for CO2 absorption processes. The effect of the different amino composition on the CO2 capture mechanism was evaluated by identifying and quantifying the species formed during the capture process through an accurate 13C NMR speciation study. The results obtained showed that all formulated sorbents have higher desorption performance and require less energy for regeneration than conventional aqueous MEA, confirming that blending different alkanolamines has the potential to improve CO2 capture. In particular, blend-2 can be regarded as a promising sorbent for implementation in commercial systems, as it performed a desorption rate up to 5 times higher than conventional aqueous MEA, combined with a significantly lower relative heat duty for regeneration (41.5%) and lower operating costs for CO2 capture.