(348j) Coupling of 1-Ethyl-3-Methylimidazolium Cation Based Room Temperature Ionic Liquids with Membrane Contactor; Post Combustion CO2 Capture

Post-combustion CO₂-capture is a convenient way to control the anthropogenic increase of CO₂. The coupling of a hollow fiber membrane contactor (MC) with ionic liquids (ILs) for CO₂ extraction from gaseous fluxes is an innovative intensified process coupling the advantages of membrane technology with unique properties of ILs such as high CO₂ solubility and negligible vapor pressure.

Room temperature ILs namely 1-ethyl-3-methylimidazolium methyl sulfate ([emim][MeSO₄]), 1-ethyl-3-methylimidazolium dicyanamide ([emim][DCA]), 1-ethyl-3-methylimidazolium ethyl sulfate ([emim][EtSO₄]) and 1-ethyl-3-methylimidazolium acetate ([emim][AC]) were coupled with mesoporous hydrophobic polypropylene MC (Liqui-Cel^®, USA), for CO₂ absorption and desorption considering a closed loop recirculation of ILs on the shell side. IL was recirculated during the absorption operation until reaching pseudo-steady state. ILs and membranes were characterized before to confirm no wetting conditions following Laplace-Young equation. The setup was tested against various operating conditions. Absorption performance of the coupled IL-MC setup, variation of absorption kinetics with CO₂ concentration, experimental mass transfer coefficients (K_exp) and absorption capacities of the ILs were thoroughly investigated in this work. Finally, a pseudo-steady state dynamic mathematical model was developed to compare (with experiments) and extend the study.

The Initial/pseudo-steady state K_exp recorded for ILs [emim][MeSO₄], [emim][DCA], [emim][EtSO₄] and [emim][AC] were 9.28*10^-6/0.22*10^-6 m.s^-1, 9.27*10^-6/0.32*10^-6 m.s^-1, 23.31*10^-6/0.59*10^-6 m.s^-1 and 46.40*10^-6/0.44*10^-6 m.s^-1, respectively. Gradual increase in the CO₂ concentration of the IL has strongly influenced the absorption process which is very fast in the beginning and becomes very slow at pseudo-steady state. Based on the overall CO₂ capture performance of the coupled system the ILs can be ranked as [emim][AC]>[emim][EtSO₄]>[emim][DCA]>[emim][MeSO₄]. The developed dynamic model showed very close agreement with the experiments (Figure 1 below).

As conclusions it can be asserted that findings of experimental and modelling results suggests that in spite of the difference in the absorption performance between ILs presented here, all are potential absorbents for CO₂ in MCs.