Mutual and Self-Diffusivities in Binary Mixtures of [EMIM][B(CN)₄] with Dissolved Gases by Using Dynamic Light Scattering and Molecular Dynamics Simulations

Abstract

Ionic liquids (ILs) are possible working fluids for the separation of carbon dioxide (CO2) from flue gases. For evaluating their performance in such processes, reliable mutual-diffusivity data are required for mixtures of ILs with relevant flue gas components. In the present study, dynamic light scattering (DLS) and molecular dynamics (MD) simulations were used for the investigation of the molecular diffusion in binary mixtures of the IL 1-ethyl-3-methylimidazolium tetracyanoborate ([EMIM][B(CN)4]) with the dissolved gases carbon dioxide, nitrogen, carbon monoxide, hydrogen, methane, oxygen, and hydrogen sulfide at temperatures from 298.15 to 363.15 K and pressures up to 63 bar. At conditions approaching infinite dilution of a gas, the Fick mutual diffusivity of the mixture measured by DLS and the self-diffusivity of the corresponding gas calculated by MD simulations match, which could be generally found within combined uncertainties. The obtained diffusivities are in agreement with literature data for the same or comparable systems as well as with the general trend of increasing diffusivities for decreasing IL viscosities. The DLS and MD results reveal distinctly larger molecular diffusivities for [EMIM][B(CN)4]-hydrogen mixtures compared to mixtures with all other gases. This behavior results in the failure of an empirical correlation with the molar volumes of the gases at their normal boiling points. The DLS experiments also showed that there is no noticeable influence of the dissolved gas and temperature on the thermal diffusivity of the studied systems.

Liquid Viscosity and Surface Tension of n-Dodecane, n-Octacosane, Their Mixtures, and a Wax between 323 and 573 K by Surface Light Scattering

“…A sample cell consisting of stainless steel and having the same outer dimensions as that employed in our previous light scattering measurements from the bulk of fluids − was used. Compared to the latter investigations, the special feature of the cell used in this study is that it provides a larger effective surface length of 7 cm due to the larger total inner volume of about 105 mL instead of 40 mL.…”

Diffusivities in Binary Mixtures of n-Hexane or 1-Hexanol with Dissolved CH4, Ne, Kr, R143a, SF6, or R236fa Close to Infinite Dilution

“…Dynamic light scattering (DLS) has been proven to be an excellent tool for the simultaneous and accurate determination of a and D 11 in liquids with dissolved gases under various thermodynamic conditions. − In contrast to conventional techniques, DLS does not require calibration and is applied at the macroscopic thermodynamic equilibrium. Therefore, no macroscopic gradient, which may lead to a convective/advective mass transport besides the molecular one, must be applied.…”

Dissolution of Trihexyltetradecylphosphonium Chloride in Supercritical CO2

“…For almost two decades, many groups have studied CO 2 interactions with ILs, which has led to IL applications such as CO 2 capture [26,27], catalyst recycling [23,28] and nanomaterial processing [1]. Much of the work to date, both experimental and theoretical, has focused nearly exclusively on various 1-alkyl-3-methyl imidazolium cations in combination with a variety of anions, where the cation alkyl chains used have been typically from C 2 to C 6 [1,23,[28][29][30][31][32][33][34][35][36][37][38][39][40][41][42]. This body of literature can be summarized by two main goals: (1) the measurement of the phase behavior of CO 2 dissolved in ILs; and (2) the quantitation of CO 2 solubility in a bulk phase IL.…”