Hydrophobic Functional Deep Eutectic Solvents Used for Efficient and Reversible Capture of CO.

CO emission from flue gas is an important issue threatening human survival. Deep eutectic solvents (DESs), which have many unique properties, have been studied for CO capture. However, water can be absorbed by DESs during the absorption of CO, which may increase the energy cost during the desorption of CO. In this work, a new kind of hydrophobic functional DES formed by polyamine hydrochloride and thymol was synthesized and used for CO capture. It had been found that these DESs could efficiently capture CO even at low partial pressures. The CO capacity of [TEPA]Cl-thymol ( / = 1:3) was high up to 1.355 mol CO/mol DES at 40 °C and 101.3 kPa. Interestingly, these DESs were still hydrophobic after saturated with CO. The CO absorption capacity increased with a decrease of temperature and an increase of CO partial pressure. Regeneration results showed that no obvious loss in the capacity could be found after five absorption/desorption cycles of these DESs. The Fourier transform infrared (FT-IR) spectra indicated that CO could interact with amino in the DESs by the formation of carboxylate. Moreover, the equilibrium constant and Henry's law constant in chemical absorption and physical absorption were studied.