Experimental study on CO₂ absorption in novel biphasic solvents and CO₂ desorption by novel direct non-aqueous gas stripping process

In this work, we proposed aqueous blends of 2-(diethylamino)-ethanol (DEEA) and monoethanolamine (MEA) or 2-((2-aminoethyl) amino) ethanol (AEEA) as the biphasic solvent for CO2 capture. Aqueous DEEA-AEEA solvent maintained an effective CO2 loading range (0.86-3.15 mol/kg) that gives two phase at 40 ^oC. During the two-phase formation, more than 95% of the absorbed CO2 concentrated in the lower phase and the weight percentage of the lower phase was found to increase with increased total CO2 loading. Quantitative ¹³C NMR analysis indicated that AEEA reactions with CO2 dominate at the beginning of CO2 absorption and the reaction products are in forms of carbamates. Then DEEA starts to react with CO2 and the reaction products are bicarbonate and carbonate. Analysis on the phase split behavior indicated that CO2 products of carbamates and HCO3^-/CO3^2- migrated to the lower phase while DEEA and unreacted AEEA migrated to the upper phase.