Magdalena Bendová

Phase Behaviour, Interactions, and Structural Studies of (Amines+Ionic Liquids) Binary Mixtures

We present a study on the phase equilibrium behaviour of binary mixtures containing two 1-alkyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}imide-based ionic liquids, [C(n)mim] [NTf(2)] (n=2 and 4), mixed with diethylamine or triethylamine as a function of temperature and composition using different experimental techniques. Based on this work, two systems showing an LCST and one system with a possible hourglass shape are measured. Their phase behaviours are then correlated and predicted by using Flory-Huggins equations and the UNIQUAC method implemented in Aspen. The potential of the COSMO-RS methodology to predict the phase equilibria was also tested for the binary systems studied. However, this methodology is unable to predict the trends obtained experimentally, limiting its use for systems involving amines in ionic liquids. The liquid-state structure of the binary mixture ([C(2)mim] [NTf(2)]+diethylamine) is also investigated by molecular dynamics simulation and neutron diffraction. Finally, the absorption of gaseous ethane by the ([C(2)mim][NTf(2)]+diethylamine) binary mixture is determined and compared with that observed in the pure solvents.

Solid–liquid equilibria in systems [Cxmim][Tf2N] with diethylamine

Abstract In the present work, the solid–liquid–liquid equilibrium in the binary system of diethylamine (1) and ionic liquid (2) 1-methyl-3-ethylimidazolium bis(trifluoromethylsulfonyl)imide and solid–liquid equilibrium in system 1-methyl-3-butylimidazolium bis(trifluoromethylsulfonyl)imide was studied. Phase equilibrium was determined experimentally by means of a polythermic method. These data were then used to determine the activity coefficients for both ionic liquids. For the pure diethylamine the enthalpy of fusion was determined by differential scanning calorimetry, because to the best of our knowledge, this data is not yet reported in the open literature, a contrario of pure ionic liquids tested during this work.

Introduction on Special Issue: Ionic Liquids

One may ask what is the reason for this special issue of the Journal of Solution Chemistry being dedicated both to the fashionable topic of ionic liquids and to the memory of Prof. Eduard Hala. A prominent personality and internationally renowned thermodynamicist, Prof. Hala is the author of more than 50 original papers and, more importantly, of two seminal and timeless monographs [1, 2]. In the early 1960s, while he was still a young pedagogue at the Institute of Chemical Technology Prague, he wrote with his faculty colleague and longtime friend Arnost Reiser the first modern Czech textbook of physical chemistry that was inspired by similar university textbooks published in English. Later, he summarized his deep knowledge in a book entitled Vapor–Liquid Equilibria, which is commonly called ‘‘a chemical engineer’s cookbook’’. Shortly after its publication in Czech, Vapor–Liquid Equilibria was translated into English and published by Pergamon Press. Since then this publication has become compulsory reading material of every thermodynamicist and engineer dealing with distillation processes. Prof. Hala was also among the first in Czechoslovakia to have grasped the importance of computer programming in science and later of the increasing significance of statistical thermodynamics. As an outstanding university educator and co-founder with Prof. Reiser of the so-called Prague School of Physical Chemistry, Prof. Hala is therefore worth remembering time and time again. Prof. Hala passed away in 1989 and even though ionic liquids were already a known class of compounds at that time, a pronounced interest in their properties and applications only started to show itself in the early 1990s. However, Prof. Hala was known throughout

Ionic Liquids as Thermal Energy Storage Materials: On the Importance of Reliable Data Analysis in Assessing Thermodynamic Data

In spite of many statements on the application potential of ionic liquids, these organic salts present both advantages and drawbacks for their possible use in real processes. Nevertheless, they are still an undeniably fascinating class of compounds, both from the fundamental point of view and as promising task-specific materials. For instance, reliable thermal property data seem to be significantly lacking for pure ionic liquids. In addition, to assess the application potential of any material or process, a reliable analysis of experimental data is of key importance, not only to obtain recommended data, but also to be able to identify patterns in structure–property relationships, even if those may not seem evident at first sight. The aim of this work is to assess the potential application of a series of 1-alkyl-3-methylimidazolium saccharinate ionic liquids (alkyl standing for butyl, hexyl, octyl, and decyl) in thermal energy storage. To this end, heat capacity and energy density were determined experimentally by means of differential scanning calorimetry (DSC) and oscillating-tube densitometry. The experimental data were then analyzed by means of advanced data analysis methods based on mathematical gnostics. Based on the thermodynamic data and theory of measurement, mathematical gnostics is a novel non-statistical approach towards data uncertainty. As such it enables us to evaluate measurement uncertainty of statistically non-significant data sets containing as few as four data points. Also, using robust regression algorithms along a gnostic influence function, functional dependencies and structure–property patterns can be reliably determined.

Liquid Phase Behavior in Systems of 1-Butyl-3-alkylimidazolium bis{(trifluoromethyl)sulfonyl}imide Ionic Liquids with Water: Influence of the Structure of the C5 Alkyl Substituent

In the present paper a study of the liquid phase behavior in aqueous systems of imidazolium-based ionic liquids (ILs) with the bis{(trifluoromethyl)sulfonyl}imide anion is addressed. To highlight the influence of the C5 alkyl side group structure on their properties, a series of ILs with linear, branched, and cyclic substituents was studied. As was already shown in our previous work, very subtle changes in the cation structure at the molecular scale can have a significant and unexpected impact on the bulk properties. Therefore, in this work, the mutual solubilities of 1-butyl-3-alkylimidazolium bis{(trifluoromethyl)sulfonyl}imide ionic liquids and water were studied, both experimentally and by modeling, at atmospheric pressure as a function of temperature from 293.15 to 328.15 K. The solubilities of the ionic liquids in water are very low, typically around 10−5 mole fraction units and were measured by a direct analytical method, making use of UV–Vis spectrophotometry. The solubilities of water in the ionic liquids were found to be around 0.20 mole fraction units and were measured using the cloud-point method. In addition to the experimental data, the liquid–liquid equilibria in the systems were modeled using the COSMO-RS methodology. Phase diagrams and the critical solution points were also estimated by applying the universal scaling laws based on the 3D Ising model, taking into account the non-linearity of the diameter and crossover to mean-field behavior.