Selection and characterization of non-ideal ionic liquids mixtures to be used in CO2 capture

Abstract

Due to the costs involved, the capture of CO 2 in post-combustion is not currently seen as economically viable. Aiming at changing the perception of post-combustion CO 2 from a costly and non-profitable process to a valuable commodity and fostering the development of the next-generation of technologies, novel solvents and their mixtures have been investigated. In this work, mixtures of non-volatile ionic liquids were screened by COSMO-RS aiming to find mixtures with positive excess volumes that could present an increased CO 2 capture by physical sorption. The most promising mixtures identified by COSMO-RS, [C 4 C 1 im][DMP] or [C 4 C 1 im][NTf 2 ] þ carboxylate-based protic ILs were characterized through the measurement of their thermophysical properties, namely density and viscosity. Both properties were measured for pure ILs and their binary mixtures at different temperatures and compositions. The temperature dependence of density of pure ILs was described using the Gardas and Coutinho model while viscosity was accurately described using the VogelÀTammannÀFulcher equation. The Redlich-Kister equation was used to predict the excess molar volumes and the non-ideality of the mixtures' viscosity was assessed using the Grunberg and Nissan mixing law. The excess molar volumes for mixtures containing [C 4 C 1 im][DMP] show large positive values all over the range of compositions and temperatures, making them good candidates for CO 2 capture. To the best of our knowledge, the excess molar volumes obtained in this work were the highest reported so far. COSMO-RS was able to correctly predict the trend of the experimental excess molar volumes for these mixtures. Regarding viscosity, mixtures of [C 4 C 1 im] [DMP] with the carboxylate-based protic ILs led to the desired viscosity decrease compared to the pure aprotic IL, and large deviations from ideality were observed. The mixing of ILs is thus an efficient way to fine-tune the properties, in this case decreasing the viscosity while increasing the sorption capacity.

Gas Solubility Using Deep Eutectic Solvents: Review and Analysis

“…However, they are not environment friendly due to their toxicity, partial degradation, high vapor pressure, corrosive byproduct formation, intensive energy consumption, and high uptake costs. Thus, scientists and engineers have developed economic absorbers or CO 2 capture technology. ,,, Among the several possibilities, ionic liquids (ILs) and deep eutectic solvents (DESs) have attracted much attention for replacing aqueous amine solutions. − …”

Encapsulated Protic Ionic Liquids as Sustainable Materials for CO2 Separation

“…Recently, the use of this family of PILs has been suggested for CO 2 capture. 35 Then, their thermophysical properties (density and viscosity), at atmospheric pressure, for different acid/base proportions were analyzed. However, despite the availability of some experimental data on CO 2 solubility in carboxylate-based PILs, 46,59−63 there are no experimental data for gas−liquid equilibrium for carboxylate-based PILs based on the N,N-diethylethanolammonium cation, despite their promising potential for gas separation, which are reported here for the first time.…”

“…ILs mixed with a range of 6 carboxylate-based PILs demonstrate higher excess molar volumes, thus foreseeing increased CO 2 solubility due to the mixtures' increased free volume and lower viscosity than that observed for the PILs. 35 However, one of the principal drawbacks of using PILs is their intrinsic viscosity, which results in low mass transfer coefficients that hinder their industrial application in conventional absorption processes and ultimately result in unfeasible large separation units. Despite the limiting properties exhibited by the ILs, researchers tend to concentrate on improving their sorption capacity, neglecting other important characteristics, such as their poor transport properties, which often make the processes not viable due to high capital and operating costs.…”

Ionic liquids as alternative solvents for energy conservation and environmental engineering

“…A new dual functionalized IL containing amine and amino acid groups in the imidazolium ring was prepared by Lu et al High CO2 absorption capability, thermal tolerance and regeneration capacity were exhibited by these ILs [60]. Recently, Martin et.al proposed a study on selection and characterization of non-ideal ionic liquids in CO2 capture [61]. A novel absorbent medium comprised of amino-functionalized ionic liquids (AFILs) dissolved in ethanol-water solvent was developed by Huang et al The solution gets separated into two phases after CO2 absorption and this phase transition behavior depends on the water-ethanol ratio [59].…”