Thermophysical properties of ionic liquids (original) (raw)
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Predictive Group Contribution Models for the Thermophysical Properties of Ionic Liquids
Ionic liquids have been the object of intense interest from both academic and industrial research groups aiming at a wide range of applications in novel processes and products. The knowledge of their thermophysical properties, or the ability to estimate them, is often required for the design of these processes and products. However, experimental data for many properties are in short supply and often contradictory among various sources available. Based on experimental data collected from the literature, predictive group contribution models were developed after a critical analysis of the data for various thermophysical properties, viz. density, viscosity, surface tension, speed of sound, refractive index, heat capacity, electrical conductivity, thermal conductivity, isobaric expansivity, and isothermal compressibility, of various families of ionic liquids. The results of the proposed models show average absolute relative deviations generally of the same order as the experimental accuracy of the data itself. These rapid and facile predictive models are very easy to use, can provide predictions of property values for the new ionic liquids, and also allow them to be extended to new groups of cations and anions as further data become available.
Predictive methods for the estimation of thermophysical properties of ionic liquids
RSC Advances, 2012
While the design of products and processes involving ionic liquids (ILs) requires knowledge of the thermophysical properties for these compounds, the massive number of possible distinct ILs precludes their detailed experimental characterization. To overcome this limitation, chemists and engineers must rely on predictive models that are able to generate reliable values for these properties, from the knowledge of the structure of the IL. A large body of literature was developed in the last decade for this purpose, aiming at developing predictive models for thermophysical and transport properties of ILs. A critical review of those models is reported here. The modelling approaches are discussed and suggestions relative to the current best methodologies for the prediction of each property are presented. Since most of the these works date from the last 5 years, this field can still be considered to be in its infancy. Consequently, this work also aims at highlighting major gaps in both existing data and modelling approaches, identifying unbeaten tracks and promising paths for further development in this area.
Comptes Rendus Chimie, 2012
The special properties of ionic liquids (ILs), such as very low vapor pressure, large liquidus range, high thermal stability, high ionic conductivity, and large electrochemical window, among others, make these fluids of special interest for several applications. Additionally, since thousand of combinations between cations and anions can be done, ionic liquids can be designed for almost any specific use [1]. Although the first room temperature ionic liquid was discovered more than a century ago, it has been during the last 20 years that these extraordinary fluids have attracted the attention of the scientific community [2]. Current studies on ionic liquids cover a variety of subjects such as electrochemistry, separation science, chemical synthesis, catalysis and pharmaceuticals, The use of ILs as thermal fluids, lubricants, catalysts and solvents, and their application to biomass processing, biphasic chemical processes, photovoltaic cells, fuel cell electrolytes, synthesis of inorganic nanomaterials, extraction of organic compounds, enzymatic reactions, separation of inorganic materials, and many others, are being continuously discussed in the literature and new advances appear every day [3-9]. Classic books such as those of Wypych [10], Wasserscheid and Welton [11] and Koel [12] contain abundant information about properties, uses and applications of ionic liquids. Also of the many recent papers describing the multiple applications of ionic liquids the recent review of Giernoth [13] provides an overview of the wide variety of applications of ILs beyond their use as solvents and discusses the task-specific characteristic of ionic liquids. Also, Aparicio et al. [14] present a good account on thermophysical properties of pure ionic liquids. These authors analyze the type of thermophysical properties data
Computation of normal melting temperature of ionic liquids using a group contribution method
Fluid Phase Equilibria, 2012
In this communication, a comprehensive literature survey has been performed to provide a data set for the normal melting temperature (T m ) of 799 ionic liquids (ILs) from various 143 references. Using this data set, an accurate group contribution method has been developed to estimate the T m of ILs. The model employs a total of 80 sub-structures to predict the T m of ILs. To better distinct the effects of anion and cation on the latter property, 31 sub-structures related to chemical structure of anion, and 49 substructures related to the chemical structure of cation have been implemented. The results of this method show a low average relative deviation (AARD%) of 5.82% for a data set including 799 ILs.
Determination of Physical Properties of Ionic Liquids Using Molecular Simulations
2010
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Physical Properties of Ionic Liquids: Database and Evaluation
Journal of Physical and Chemical Reference Data, 2006
A comprehensive database on physical properties of ionic liquids ͑ILs͒, which was collected from 109 kinds of literature sources in the period from 1984 through 2004, has been presented. There are 1680 pieces of data on the physical properties for 588 available ILs, from which 276 kinds of cations and 55 kinds of anions were extracted. In terms of the collected database, the structure-property relationship was evaluated. The correlation of melting points of two most common systems, disubstituted imidazolium tetrafluoroborate and disubstituted imidazolium hexafluorophosphate, was carried out using a quantitative structure-property relationship method.
Thermophysical and transport properties of ionic liquids are required for the design of processes and products. Yet the experimental data available are scarce and often contradictory. Based on experimental data collected from the literature, group contribution methods were developed for the estimation of viscosity, electrical conductivity, thermal conductivity, refractive index, isobaric expansivity, and isothermal compressibility, of various families of ionic liquids. Using the Stokes–Einstein relation a correlation for the self-diffusion coefficients with the viscosity is also proposed. The results of the proposed models show average absolute relative deviations generally of the same order of the experimental accuracy of the data. They are easy to use and can provide predictions of property values for ionic liquids never previously studied. The group contribution basis of these models will allow them to be extended to new groups of cations and anions as further data became available. © 2009 American Institute of Chemical Engineers AIChE J, 2009