Mass-transfer kinetics of CO2 in a hybrid choline-2-pyrrolidine-carboxylic acid/polyethylene glycol/water absorbent

Abstract

Understanding the mass-transfer kinetics of CO2 in novel hybrid absorbents with physical and chemical contributions is essential for process design and evaluation. In this study, the liquid-side mass-transfer coefficients (kL) and second-order reaction rate constants (k2) of CO2 in hybrid absorbents (namely, choline-2-pyrrolidine-carboxylic acid salt/polyethylene glycol/water ([Cho][Pro]/PEG200/H2O)) were determined. The kL values for the hybrid absorbents were obtained from the CO2 diffusion coefficients (DCO2) and the kL values in PEG200/H2O. The DCO2 value was calculated from the density and viscosity of the hybrid absorbents, whereas the kL values in PEG200/H2O were measured experimentally. The k2 values of CO2 in the hybrid absorbents were estimated according to the reaction mechanism, the enhancement factor, and the kL values, and compared with those of other commercialized absorbents. The results showed that 30 wt% [Cho][Pro] + 70 wt% H2O had the highest kL and k2 values at atmospheric pressure, whereas the values of kL and k2 of CO2 in 30 wt% [Cho][Pro]/H2O + PEG200 were comparable to those in diethanolamine aqueous and amino-functionalized ILs. The hybrid absorbent of [Cho][Pro]/PEG200/H2O could be promising for CO2 separation considering its thermodynamic and kinetic properties.