Highly efficient CO removal by active cuprous-based ternary deep eutectic solvents [HDEEA][Cl] + CuCl + EG

Abstract

Carbon monoxide (CO) is a kind of impurity gas in hydrogen (H2), resulting to catalyst poisoning in proton-exchange-membrane fuel cells (PEMFCs). On the other hand, CO is harmful to human health due to its colorlessness, odorlessness and high toxicity. In this contribution, a series of active cuprous-based ternary deep eutectic solvents (DESs) with 2-diethylaminoethanol chloride ([HDEEA][Cl]) plus cuprous chloride (CuCl) plus ethylene glycol (EG) at different molar ratios (1:1:4, 1:1:2 and 1:1:1) were designed and prepared. Physical properties such as density and viscosity of these DESs were measured at different temperatures. CO capture by these DESs were investigated at different concentrations of CO and different temperatures. It was found that the capture capacities of 0.203 and 0.564 mol CO per mole DES could be reached by [HDEEA][Cl] + CuCl + EG with n[HDEEA][Cl]:nCuCl:nEG = 1:1:4 at 293.2 K and 1 bar or 5 bar, respectively. FT-IR method was used to investigate the mechanism of CO removal. These results suggested that the presence of Cu(I) is crucial for efficient capture of CO by these ternary DESs while − OH groups and EG could release the activity of Cu(I). Furthermore, the thermodynamic properties such as the Gibbs free energy change (ΔG), enthalpy change (ΔH), and entropy change (ΔS) for CO capture by [HDEEA][Cl] + CuCl + EG (1:1:4) were obtained, and ΔH was the main driving force for CO capture.