CO2/H2 separation by amino-acid ionic liquids with polyethylene glycol as co-solvent

Abstract In this work polyethylene glycol 400 (PEG400) was introduced as a co-solvent to intensify CO 2 separation and reduce the viscosity of amino-acid ionic liquids (AAILs) while maintain their unique properties, i.e. undetectable vapor pressure, high thermal stability and excellent CO 2 solubility. The thermal gravimetric analysis indicated that AAILs, PEG400 and their blend solvents were stable at above 523 K and showed negligible weight loss at 373 K for 300 min. The viscosity of the mixed solvents decreased to be about half of that of pure AAILs at 298 K. The CO 2 solubility in the mixed solution was measured over a range of pressures from 100 to 1700 kPa and of temperatures from 333.15 to 413.15 K at 40 K intervals. The ideal CO 2 /H 2 selectivity reached 110 at 333.15 K and 100 kPa. PEG400 as a co-solvent may have created a better gas-liquid interface, which promotes the mass transfer and intensifies the CO 2 sorption in AAILs. A CO 2 absorption mechanism in AAILs-PEG400 was proposed accordingly to explain the intensification effect with evidence from the FTIR results.