Rich Ether-Based Protic Ionic Liquids with Low Viscosity for SelectiveAbsorption of SO2 through Multisite Interaction

Four low-viscosity protic ionic liquids (PILs) with thetertiary amine and rich ether skeletons are designed for selectiveabsorption of SO2. To evaluate the selective absorption of SO2by thesePILs, the solubilities of SO2,CO2, and H2S are measured in thetemperature range of 303.2-333.2 K and pressures up to 120 kPa by avolumetric method, respectively. The absorption of SO2by [TMEA]-[MOAc] at 303.2 K and 101.3 kPa was found to be 10.424 molmiddotkg-1(4.310 molmiddotmol-1), and the ideal selectivity of SO2/CO2was 86.83. Inaddition, the solubility data arefitted using a reaction equilibriumthermodynamic model to obtain thermodynamics parameters includingGibbs free energy change (Delta rGm), enthalpy change (Delta rHm,Delta phyHm,Delta chemHm), and entropy change (Delta rSm). The mechanism of SO2absorption by [TMEA][MOAc] is also investigated by FTIR andNMR analyses. Mechanistic and thermodynamic studies suggest that the high SO2absorption is attributed to the O-SO2multisitephysical interaction. These ether-rich PILs are considered as a promising absorber because of their high SO2solubility, good cyclingperformance, and low viscosity before and after absorption.