Development of a Promising Biphasic Absorbent for Postcombustion CO2 Capture: Sulfolane + 2-(Methylamino)ethanol + H2O

A new sulfolane/secondary amine biphasic absorbent, sulfolane/2-methylaminoethanol (MAE) solution, was developed for postcombustion CO2 capture (PCC). Surprisingly, using a 4M/5M sulfolane/MAE solution saves about 60% energy consumption (EC) for CO2 stripping when compared with traditional aqueous 5M monoethanolamine (MEA) solutions. First, we theoretically proved that MAE in sulfolane-based biphasic solution improves the CO2 absorption rate with high CO2 loading at the phase-changing point, which could be energy-saving for CO2 stripping. Based on a comprehensive comparison of the phase-changing behavior, nuclear magnetic resonance (NMR) spectra, absorption rate, and desorption performance, the 4M/5M sulfolane/MAE was determined to be the optimal molar ratio among six sulfolane/MAE biphasic solutions for CO2 capture. In addition, the absorption and desorption experiments with various temperatures revealed that relatively low temperature (ranging from 110 to 120 °C) was favorable for CO2 removal and energy-saving. Furthermore, the 4M/5M sulfolane/MAE solution achieved a very low energy consumption (EC) compared with that of 5M MEA solution, and the stripped CO2 amount is similar to that of 5M MEA and 5M MAE solutions.