Mass‐transfer rate enhancement for CO₂ separation by ionic liquids: Theoretical study on the mechanism

Abstract

To promote the development of ionic liquid (IL) immobilized sorbents and supported IL membranes (SILMs) for CO 2 separation, the kinetics of CO 2 absorption/desorption in IL immobilized sorbents was studied using a novel method based on nonequilibrium thermodynamics. It shows that the apparent chemical-potential-based mass-transfer coefficients of CO 2 were in three regions with three-order difference in magnitude for the IL-film thicknesses in microscale, 100 nm-scale, and 10 nm-scale. Using a diffusion-reaction theory, it is found that by tailoring the IL-film thickness from microscale to nanoscale, the process was altered from diffusion-control to reaction-control, revealing the inherent mechanism for the dramatic rate enhancement. The extension to SILMs shows that the significant improvement of CO 2 flux can be obtained theoretically for the membranes with nanoscale IL-films, which makes it feasible to implement CO 2 separation by ILs with low investment cost.

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