Investigation of the Thermophysical Properties of AMPS-Based Aprotic Ionic Liquids for Potential Application in CO₂ Sorption Processes

The thermophysical properties such as density, refractive index, and viscosity of five aprotic ILs bearing imidazolium (1-ethyl-3-methylimidazolium [emim], 1-butyl-3-methylimidazolium [bmim], 1-benzyl-3-methylimidazolium [bnmim]), pyrrolidinium (1-butyl-1methylpyrrolidinium [bmpyr]), and pyridinium (<i>N</i>-butylpyridinium [bpyn]) cations with 2-acryloamido-2-methylpropanesulfonate [AMPS] anion were studied, and their effect on CO₂ solubility was explored. The density and viscosity were determined within the temperature range of (293.15 to 363.15) K at atmospheric pressure, while refractive indices were measured within the temperature range of (288.15 to 333.15) K. Among imidazolium cations, increasing the side chain length resulted in increased refractive index and viscosity with a corresponding decrease in density. In the presented ILs, [emim]­[AMPS] showed the highest density and least viscosity over the entire temperature range and an enhanced CO₂ dissolution of 0.40 mole fraction at 1 MPa was observed at 298.15 K. Moreover, the Henry’s constant of [emim]­[AMPS] was determined to be 1.957 MPa which was 49.5, 65.5, 21, and 53% less than [bmim]­[AMPS], [bnmim]­[AMPS], [bmpyr]­[AMPS], and [bpyn]­[AMPS], respectively. The present study provides a better understanding of the structure–activity relationship between CO₂ sorption and physicochemical properties of studied ILs