Optimization and Characterization of an Amino Acid Ionic Liquid and Polyethylene Glycol Blend Solvent for Precombustion CO2 Capture: Experiments and Model Fitting

Abstract

Amino acid ionic liquids are green solvents with low toxicities and properties suitable for precombustion CO2 capture, such as high CO2 absorption, good thermal stability, and negligible vapor pressure. However, their high viscosities and relatively high costs have hampered their industrial applications. In this work, we systematically studied the amino acid ionic liquid tetrabutylphosphonium glycinate ([P4444][Gly]) and its blends with the low-cost and less viscous cosolvent poly(ethylene glycol) (PEG400). The concentration of the blend solvent was optimized with respect to CO2 solubility, regeneration efficiency, and cyclic capacity. The solubilities of CO2 in [P4444][Gly], PEG400, and their blends of four different concentrations were measured experimentally in the temperature range of 60–140 °C and up to a pressure of 17 bar. The results showed that the CO2 solubility increased with increasing ionic liquid concentration in the blend and decreased with increasing temperature. The optimum CO2 absorption...