Preparation of ionic liquids amine hybrid solvents, characterization for CO2 absorption, and kinetic performance

Abstract

The thermo-physical characteristics of an ionic liquid-amine hybrid solvent were studied in this work as a result of its potential use in the CO2 absorption process. The hybrid solvents were developed by mixing 30 wt% MDEA with ionic liquid at different concentrations of 5 wt%, 10 wt%, 15 wt% and 20 wt%. Three imidazolium-based ILs were investigated: 1-butyl-3-methylimidazolium dicyanamide [bmim][DCA], 1-butyl-3-methylimidazolium acetate [bmim][Ac] and 1-butyl-3-methylimidazolium trifluoromethanesulfonate [bmim][TfO. Aqueous ionic liquid-amine hybrid solvent's density, surface tension, refractive index, viscosity and were studied between 25 °C and 70 °C with a regular interval of 5 °C. Whereas the influence of temperature on viscosity is negligible beyond 65 °C and the influence of temperature changed certain physicochemical properties. Furthermore, high-pressure solubility tests were conducted at a fixed temperature of 30 °C to determine the solubility of CO2 in hybrid media at pressures ranging from 2 bar to 50 bar. The results showed that the CO2 solubility of the different ionic liquid-amine hybrid systems decreases in the following sequence: [bmim][TfO] + MDEA > [bmim][DCA] + MDEA > [bmim][Ac] + MDEA. It was also found out that the optimum concentration of ionic liquids in the solution is 10 wt%. The kinetics study of the hybrid solvents was studied as a function of concentration, and experimentally determined that 10 wt% [bmim][TfO] exhibited the fast CO2 absorption kinetics. The kinetics performance study was further conducted as a function of pressure, and the highest absorption rate was recorded at 50 bar as expected. Overall, the addition of ionic liquids was verified to improve the CO2 absorption and thus it was reported that ionic liquid-amine hybrid solvent is an auspicious solvent for CO2 removal in the future.