High regeneration efficiency and low viscosity of CO2 capture in a switchable ionic liquid activated by 2-amino-2-methyl-1-propanol

Switchable ionic liquids (SILs) are novel green non-aqueous absorbents for energy-efficient post-combustion CO2 capture. However, their regeneration efficiency and viscosity still need to be improved. SILs can be activated by some alkylol amines to improve their regeneration efficiency and reduce viscosity. In this work, mixtures of the SIL 1,8-diazabicyclo-[5.4.0]-undec-7-ene (DBU)/ethanol and 2-amino-2-methyl-1-propanol (AMP) were used for CO2 capture. The constitution of the absorbent was optimized. Absorption and regeneration were investigated, and the detailed reaction mechanisms for CO2 capture were analyzed using 13C NMR and FTIR. The results demonstrated that CO2 could be absorbed to form carbonates in two ways. On the one hand, CO2 reacted with DBU and ethanol to directly form carbonates. On the other hand, CO2 initially reacted with AMP to form carbamates, and then, the carbamates reacted with ethanol to form carbonates. The CO2 loading of the optimized absorbent was 2.98 mol kg−1. The saturated absorbent began to desorb at 80 °C, and the regeneration efficiency reached 99.3% when the temperature rose to 120 °C. After five cycles, the regeneration efficiency remained over 90%. Compared to DBU/ethanol, the regeneration efficiency of the DBU/AMP/ethanol mixtures was significantly better, while the viscosity was greatly reduced, which is beneficial for the industrial application.