Ten years of research on phase separation absorbents for carbon capture: Achievements and next steps

Since the first disclosure of a patent on biphasic CO2 capture absorbent in 2005, more and more research work has been carried out worldwide looking for new biphasic systems and expanding the earlier achievements. There are two types of biphasic absorbent systems: amine dissolved in alcohol, i.e., non-aqueous system; and less soluble amines (alkanolamines or lipophilic amines, single amine or a mixture of amines) dissolved in water, i.e., aqueous system. Phase separation could happen at absorption temperature or at higher temperature, resulting in a CO2-rich phase and a CO2-lean phase. Only the CO2-rich phase will be regenerated, rendering a smaller regenerator and lower regeneration energy consumption. Some of the biphasic absorbent systems show lower regeneration temperatures and higher regeneration depth compared to aqueous MEA (monoethanolamine), indicating even more potential merits. In this paper, the previous R&D results and data are summarized and reviewed. Future directions for research and development are discussed.