Molecular simulation and experimental study of CO2 absorption in ionic liquid reverse micelle.
The structure and dynamics for CO2 absorption in ionic liquid reverse micelle (ILRM) were studied using molecular simulations. The ILRM consisted of 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]) ionic liquid (IL) as the micelle core, the benzylhexadecyldimethylammonium ([BHD](+)) chloride ([Cl](-)) was the cationic surfactant, and benzene was used as the continuous solvent phase in this study. The diffusivity values of this ILRM system were also experimentally determined. Simulations indicate that there is ion exchange between the IL anion ([BF4](-)) and the surfactant anion ([Cl](-)). It was also found that the [bmim][BF4] IL exhibits small local density at the interface region between the IL core and the [BHD](+) surfactant cation layer, which leads to a smaller density for the [bmim][BF4] IL inside the reverse micelle (RM) compared with the neat IL. These simulation findings are consistent with experimental results. Both our simulations and experimental results show that [bmim][BF4] inside the RM diffuses 5-26 times faster than the neat IL, which is partly due to the fast particle diffusion for the ILRM nanodroplet (IL and surfactant) as a whole in benzene solvent compared with neat [bmim][BF4] diffusion. Additionally, it was found that [bmim][BF4] IL solved in benzene diffuses 2 orders of magnitude faster than the neat IL. Lastly, simulations show that CO2 molecules are absorbed in four different regions of the ILRM system, that is, (I) in the IL inner core, (II) in the [BHD](+) surfactant cation layer, (III) at the interface between the [BHD](+) surfactant cation layer and benzene solvent, and (IV) in the benzene solvent. The CO2 solubility was found to decrease in the order II > III ∼ IV > I, while the CO2 diffusivity and permeability decrease in the following order: IV > III > II > I.
U.S. Department of Energy , National Energy Technology Laboratory, Pittsburgh, Pennsylvania 15236, United States.
Wei
W
Shi
Lei
L
Hong
Krishnan
K
Damodaran
Hunaid B
HB
Nulwala
David R
DR
Luebke