Bulk-Fluid Solubility and Membrane Feasibility of Rmim-Based Room-Temperature Ionic Liquids

Abstract

This paper shows how gas solubility can be predicted in Rmim-based room-temperature ionic liquids (RTILs).We have developed a model to illustrate that ideal, single-gas solubility in Rmim-based RTILs is primarily a function of molar volume of the RTIL. This method is used to estimate bulk-fluid gas solubility, showing that for Rmim-based RTILs there is a particular molar volume where a maximum amount of gas per volume of RTIL occurs at a given pressure and temperature. This method is also used to estimate gas permeability and gas pair separation selectivity for ideal CO 2 /N 2 and CO 2 /CH 4 separations. A comparison to traditional polymer membranes utilized in these separations is included in the form of a "Robeson plot".

Gas permeabilities, solubilities, diffusivities, and diffusivity correlations for ammonium-based room temperature ionic liquids with comparison to imidazolium and phosphonium RTIL data

“…This trend is consistent with the trend predicted by Camper et al [10], as the molar volume increases the selectivity decreases. For alkene/alkane separations the imidazolium-based RTILs appear to have an advantage over the phosphonium-RTILs report in our work.…”

Study on Gas Permeation and CO2 Separation through Ionic Liquid-Based Membranes with Siloxane-Functionalized Cations

“…The CH 4 and N 2 solubilities are always significantly lower than that of CO 2 amongst the SILMs studied, which is in agreement with reported results for other SILMs, in which the CO 2 separation is mainly governed by gas solubility differences in the IL. From Figure 3 [52][53][54] and in brief all the models recognized that CO 2 solubility increases by increasing the IL molecular weight, molar volume and free volume. 1 Looking at the CO 2 solubility plotted in Figure 3 According to Figure 5(a), the gas permeabilities significantly increase from 40 to 60 wt% of free siloxane-functionalized IL incorporated into the PIL-IL membranes.…”

CO2 separation applying ionic liquid mixtures: the effect of mixing different anions on gas permeation through supported ionic liquid membranes

“…This means that the Camper Model is not a general model for imidazolium-based ILs, as claimed by the authors but, in fact, limited by the anion nature of the ILs used in its derivation or, in other words, limited to ILs where CO 2 physical solubility occurs. Deviations to the Camper Model, 60 and also to the Universal Model, 61 were observed for the CO 2 /CH 4 solubility selectivity in imidazolium ILs combining alkylsulfate and alkylsulfonate anions. 65 The authors correlated these deviations with the low solubility of CH 4 in these ILs, which was explained using Kamlet-Taft bparameter (the hydrogen bond donor capacity) that is governed by the anion basicity.…”