Solubility and Diffusivity of CO2 in [hxmim][NTf2], [omim][NTf2], and [dcmim][NTf2] at T = (298.15, 308.15, and 323.15) K and Pressures up to 20 bar

Abstract

Solubilities and diffusion coefficients of CO2 absorption in the ionic liquids (ILs) [hxmim][NTf2], [omim][NTf2], and [dcmim][NTf2] at temperatures of (298.15, 308.15, and 323.15) K and pressures up to 20 bar were obtained by thermogravimetric measurements using a high pressure sorption analyzer with magnetic suspension balance operating in dynamic mode. The effect of the length of the alkyl side chain of the imidazolium cation and the operating conditions on the thermodynamics and kinetics of the CO2 absorption process in ILs were evaluated. Absorption data confirmed that the CO2 solubility in ILs increases with increasing length of the alkyl side chain of the cation and with decreasing temperatures and increasing pressures. The diffusion coefficients of CO2, calculated by applying a mass diffusion model, decrease with increasing lengths of the alkyl side chain of the cation and increase with both temperature and pressure of absorption. These results illustrate the importance of considering both thermodynamic and kinetic aspects in the selection of an IL as absorbent and the operating conditions for developing absorption processes based on ILs. In addition, the empirical correlation of Wilke–Chang was successfully applied as an alternative to estimate the diffusion coefficients of the systems.