Diffusion Coefficients of CO₂ in Ionic Liquids Estimated by Gravimetry

The estimation of diffusion coefficients of CO 2 in ionic liquids by gravimetry is analyzed with the aim of establishing a measurement method that provides consistent values of diffusivity. Absorption kinetic curves of CO 2 in three common ILs were measured at different temperatures (293–323 K) and pressures (1–20 atm) by using a high pressure sorption analyzer with magnetic suspension balance operating in dynamic mode. A mass diffusion model widely used in the literature was applied to estimate effective diffusion coefficients for CO 2 –IL systems from time-dependent absorption data. The measuring conditions (IL mass, dimension of sample container, gas flow) in the dynamic absorption experiments were modified to verify the assumptions of the diffusion model. Obtained results were compared to available data. In addition, the suitability of theoretical methods commonly used for estimating diffusion coefficients of CO 2 in ILs was analyzed, in order to select a computational approach for preliminary selection of ILs with favorable transport properties for CO 2 capture.