Water-assisted absorption of CO2 by 3-amino-1-propanol: a mechanistic insight.

The mechanism of the proton transfer in the reaction between CO2 and 3-amino-1-propanol with and without water molecules is investigated quantum-mechanically. Studies revealed that water molecules and the hydroxy group of 3-amino-1-propanol explicitly participate in the proton transfer, forming carbamic acid. It is found that water has a high impact on the energetics of CO2 absorption by reducing the barrier for proton transfer. Apart from the water molecules, the hydroxy group of alkanolamine significantly affects the energetics of the reaction. Five cases involving two, three, and four protons are discussed, and it is found that the proton transfer occurs in a concerted manner that depends on the initial configuration of the reaction complex. The present study unequivocally confirms the role of water molecules in the CO2 capturing via amine-based solvents.