DBU-Glycerol Solution: A CO2 Absorbent with High Desorption Ratio and Low Regeneration Energy.

Abstract

1,8-Diazabicyclo[5.4.0]-undec-7-ene (DBU)-glycerol solution is employed as a promising CO2 absorbent. The regeneration of the CO2-loaded solution is of vital importance for its commercialization. It was investigated and compared with 30 wt % monoethanolamine (MEA). Variables affecting the absorption and desorption processes were studied, including the solvent composition, reaction temperature, and agitation. It shows that the absorption capacity for DBU-glycerol is comparable with 30 wt % MEA, and the desorption ratio for CO2-loaded DBU-glycerol mixture can reach as high as 95% in 60 min, 363 K at the 3:1 molar ratio of DBU to glycerol, while it is only 68% even after 165 min for CO2-saturated 30 wt % MEA. DBU-glycerol solution has higher cycling CO2 loading than 30 wt % MEA. Its cyclic capacity could keep above 90% after 10 cycles of absorption-desorption experiments. The desorption reaction is irreversible at the initial stage, and the reaction rate is expected as a first-order reaction from 349 to 377 K, and the apparent activation energy is 68.94 kJ/mol. Moreover, the heat duty of the reboiler during regeneration is estimated to be reduced by about 27% when compared with 30 wt % MEA.