Comparative Study for the Absorption of Carbon Dioxide in Aqueous Amine Solvents for Enhanced Loading

Aims: The current study aimed to investigate the CO2 absorption capacity of the aqueous alkanolamine, including primary, secondary, tertiary, and sterically hindered amines and polyamines, i.e., monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA) and 2-amino-2-methyl-1-propanol (AMP), tetraethylenepentamine (TEPA), triethylenetetramine (TETA), 3-(Methylamino)propylamine (MAPA), and diethylenetriamine (DETA) at 40, 60, and 80°C at 1.1 bar. Methods: An increase in reaction temperature caused a decrement in CO2 loading across the board for all solvents. The trend of CO2 loading was TEA < MEA < DEA < AMP < MAPA < DETA < TETA < TEPA at 40 ºC, TEA < DEA < MEA < AMP < MAPA < DETA < TETA < TEPA, at 60ºC and TEA < DEA < AMP < MEA < MAPA < DETA < TETA < TEPA at 80ºC. Results: The results indicated that TEPA has great potential to be utilized as an energy-efficient and non-corrosive solvent for CO2 capture since it has outperformed all other aqueous amine solvents in this present study. Furthermore, the CO2 loading of sterically hindered amine (AMP) at the same temperature was found to be higher than primary, secondary, and tertiary amines. Heat of absorption (ΔHabs) was also determined to gauge the energy requirement to regenerate absorbents for cyclic loading from an economic viewpoint. Conclusion: DETA has the highest ΔHabs = 84.48 kJ/mol. On the contrary, the long-chain tertiary amine TEA resulted in the least ΔHabs = 40.21 kJ/mol, among all other solvents. Whereas the sterically hindered amine (AMP) was observed to possess mid-range ΔHabs, i.e., 58.76 kJ/mol. Among all selected solvents, polyamines showed higher ΔHabs than other conventional amines pertaining to the precedence of TEA<AMP<DEA<MEA<TETA<TEPA<MAPA<DETA.