Novel Amino-Functionalized Ionic Liquid/Organic Solvent with Low Viscosity for CO₂ Capture

Abstract

To achieve low regeneration energy consumption and viscosity, a novel amino-functionalized ionic liquid [TEPAH][2-MI] combined with organic solvents has been proposed for CO₂ capture in this work. The results demonstrated that the absorption loading of [TEPAH][2-MI]/<i>N</i>-propanol (NPA)/ethylene glycol (EG) was 1.72 mol·mol^-1 (28 wt %, 257 g·L^-1), which was much higher than that of monoethanolamine/water, and the regeneration efficiency was maintained at 90.7% after the fifth regeneration cycle. The viscosities of the solution were only 3.66 and 7.65 mPa·s before and after absorption, respectively, which were significantly lower than those of traditional nonaqueous absorbents. The reaction mechanism investigated via ¹³C NMR and quantum calculations summarized that CO₂ first reacted with the amino group of [TEPAH]⁺ to form the carbamates through the zwitterion formation and protonation process, while CO₂ reacted with the N atom of [2-MI]^- to directly form the carbamate. Then, some of them further reacted with NPA and EG to form the carbonates. Moreover, N^π and N^τ tautomers of [TEPAH][2-MI] could convert into each other continuously when CO₂ was absorbed. During CO₂ desorption, the carbamates and carbonates reacted with AFILH⁺ to decompose and released CO₂ directly.