Ionic liquids (ILs) comprised of ammonium cations and anions of naturally occurring amino acids containing an additional amine group (e.g., lysine, histidine, asparagine, and glutamine) were examined as high-capacity absorbents for CO2. An absorption capacity of 2.1 mol CO2 per mol of IL (3.5 mol CO2 per kg IL, 13.1 wt% CO2) was measured for [N66614][Lys] at ambient temperature and about 1 mol CO2 per mol of IL at 808C (under 1 bar of CO2). This demonstrated that desorption is possible under CO2-rich conditions by temperature-swing absorption; three consecutive sorption cycles were performed with the IL. The mechanistic and kinetic study of the absorption process was further substantiated by NMR spectroscopy and in situ attenuated total reflectance FTIR for [N66614][Lys] and the homologous phosphonium-based IL [P66614][Lys]. This study revealed that carbamic acid was formed with CO2 in both ILs by chemisorption; however, the amino acid–carboxyl groups on the anion played an important—but different—catalytic role for the sorption kinetics in the two ILs. The origin of the cationic effect is speculated to be correlated with the strength of the ion interactions in the two ILs.

Hydrogen bond donating cosolvents have been shown to significantly reduce the solubility of acetaminophen (AAP) in ionic liquids containing the acetate anion. Reduced solubility arises from competition for solvation by the acetate anion and can be used for the design of advanced separation techniques, illustrated by the crystallization of AAP.

Abstract:A new strategy for capturing nitrogen oxide, NO from the gas phase is presented. Dilute NO gas is removed from the gas phase by ionic liquids at ambient conditions. The nitrate anion of the ionic liquid catalyzes the oxidation of NO to nitric acid (HNO3) by atmospheric oxygen in the presence of water. The nitric acid is absorbed in the ionic liquid up to approximately 1 mol HNO3 per mol of ionic liquid due to the formation of hydrogen bonds. The nitric acid can be desorbed by heating, regenerating the ionic liquid with excellent reproducibility. Here, time resolved in-situ spectroscopic investigations of the reaction and products are presented. The procedure reveals a new vision for removing the pollutant, NO, by absorption into a non-volatile liquid and converting it into a useful bulk chemical, HNO3.