Isolation and Structural Characterization of Bicarbonate and Carbonate Species Formed During CO2 Absorption/Desorption By a Hindered Alkanolamine

Abstract

The pathways for the CO2 absorption and desorption in an aqueous solution of a heavily hindered alkanolamine, 2-(t- butylamino)ethanol (TBAE) were elucidated by X-ray crystallographic and 13C NMR spectroscopic analysis. In the early stage of the CO2 absorption, the formation of carbonate species ([TBAEH]2CO3) was predominant along with the generation of small amounts of zwitterionic species. With the progress of the absorption, the carbonate species was rapidly transformed into bicarbonate species ([TBAEH]HCO3), and the amounts of the zwitterionic species increased gradually. During desorption at 2-elevated temperature in the absence of CO2, [TBAEH]HCO3 was found to transform into [TBAEH]2CO3, where CO3 interacts with two [TBAEH]+ via hydrogen bondings.