CO2 absorption and desorption in an aqueous solution of heavily hindered alkanolamine: structural elucidation of CO2-containing species.

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 (13)C 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 elevated temperature in the absence of CO2, [TBAEH]HCO3 was found to transform into [TBAEH]2CO3, where CO3(2-) strongly interacts with two [TBAEH](+) via hydrogen bondings.

Two-dimensional infrared correlation spectroscopy and principal component analysis on the carbonation of sterically hindered alkanolamines.

Despite the academic and industrial importance of the chemical reaction between carbon dioxide (CO(2)) and alkanolamine, the delicate and precise monitoring of the reaction dynamics by conventional one-dimensional (1D) spectroscopy is still challenging, due to the overlapped bands and the restricted static information. Herein, we report two-dimensional infrared correlation spectroscopy (2D IR COS) and principal component analysis (PCA) on the reaction dynamics of a sterically hindered amine, 2-[(1,1-dimethylethyl)amino]ethanol (TBAE) and CO(2). The formation of carbonate rather than carbamate species, which contribute to the unusual high working capacity of ∼1 mole CO(2) per mole of TBAE at 40 °C, occurs through deprotonation of the hydroxyl group, protonation on the nitrogen atom of the amino group, and formation of a carbonate species due to the steric hindrance of the tert-butyl group. In particular, PCA captures the chemical transition into a carbonate species and the main contributions of ν(CO(2)), ν(OH), ν(C - N), and ν(C=O) bands to the carbonation, while 2D IR COS verifies the interrelation of four bands and their changes. Therefore, these results provide a powerful analytic method to understand the complex and abnormal reaction dynamics as well as the rational design strategy for the CO(2) absorbents.

Anomalous thermal transition and crystallization of ionic liquids confined in graphene multilayers.

Anomalous thermal transition and crystallization behaviors of three room temperature ionic liquids (RTILs) in graphene multilayers (GMLs), in a different manner to bulk RTILs, occurred due to the molecular orientation of the confined system triggered by the complex π-π stacking and hydrogen bonding interactions.