Protic guanidine isothiocyanate plus acetamide deep eutectic solvents with low viscosity for efficient NH3 capture and NH3/CO2 separation

Abstract

Deep eutectic solvents (DES) are regarded as the second generation ionic liquids with potential application in gas capture and separation field due to negligible vapor pressure and abundant formation variation. In present work, protic guanidine isothiocyanate was selected as hydrogen bond acceptor and paired with acetamide as hydrgen bond donor to construct low viscosity DES. The DESs were characterized with phycsichemical properties and utilized in NH3 capture and NH3/CO2 separation systematically. The gas solubility enhcanced with the increasing molar ratio of GI to AT, increasing pressure, and falling temperature. The solubilities of NH3 and CO2 were correlated by Henry's law. The thermodynamic parameters were further calculated according to the temperature dependence of Henry's constants. The NH3 saturated DES could be easily recycled five times with persistent absorption performance. The ideal NH3/CO2 selectivity at 303.15 K was 151 and higher than most solvents reported in the literatures. The absorption mechanism was further deduced by NMR and F-IR spectroscopy. These DESs presented efficient NH3 absorption and selective separation performance due to good absorption performance, reversibility, and high NH3/CO2 selectivity.