Isabel Bandrés

Thermophysic comparative study of two isomeric pyridinium-based ionic liquids.

A comprehensive thermophysical study of isomeric room-temperature ionic liquids n-butyl-3-methyl-pyridinium tetrafluoroborate and n-butyl-4-methyl-pyridinium tetrafluoroborate has been performed. This paper reports various experimental data including density, speed of sound, refractive index, surface tension, isobaric molar heat capacity, and kinematic viscosity. From the experimental results, coefficients of thermal expansion, dynamic viscosities and molar refractions of the studied ionic liquids have been determined. Results have been analyzed paying special attention to the different features of the isomers and their structural differences. Several theories and empirical relations have been applied in order to predict physical properties of ionic liquids. A good agreement between experimental and calculated data has been found. Furthermore, a study about the versatility and application of the different relationships has been carried out finding that in general density and coefficients of thermal expansion can be estimated with relatively good accuracy.

Physicochemical properties of green solvents derived from biomass

Several thermophysical properties (density, refractive index, speed of sound, surface tension, dynamic viscosity, static permittivity and vapour pressure) of five compounds classified as green solvents derived from biomass (furfural, furfuryl alcohol, levulinic acid, ethyl levulinate, butyl levulinate) have been obtained from 278.15 K to 338.15 K. A comparative study has been carried out and information regarding molecular interactions and structure has been obtained.

Anion influence on thermophysical properties of ionic liquids: 1-butylpyridinium tetrafluoroborate and 1-butylpyridinium triflate.

The thermophysical properties of two pyridinium-based ionic liquids, 1-butylpyridinium tetrafluoroborate and 1-butylpyridinium triflate, have been measured. Thus, densities, refractive indices, speeds of sound, viscosities, surface tensions, isobaric molar heat capacities, and thermal properties have been experimentally determined over a wide range of temperatures. The comparison of the properties of the two ionic liquids has allowed us to analyze in detail the anion influence. Moreover, useful derived properties have been calculated from the results. On the other hand, the influence of the lack of a substituent in the cation has been evaluated when properties of 1-butylpyridinium tetrafluoroborate have been contrasted to those of 1-butyl-n-methylpyridinium tetrafluoroborate, (n = 2, 3, or 4). The study has been carried out paying special attention to interactions between ions in order to elucidate the desired relationship between properties and structural characteristics of ionic liquids.

On the viscosity of pyridinium based ionic liquids: an experimental and computational study.

A study on the viscosity of eight pyridinium based ionic liquids is reported for wide pressure and temperature ranges. Measurements were performed using an electromagnetic moving piston viscometer. Experimental data were fitted to a Tait-like equation demonstrating good correlations, which was used to calculate pressure/viscosity and temperature/viscosity coefficients. The effect of the involved anions and cation on the ionic liquid viscosity was analyzed from a molecular viewpoint using hole theory, quantum chemistry calculations using density functional theory, and classical molecular dynamics simulations. The analysis of the experimental and computational results shows the complex effects controlling viscosity of studied fluids, including strength of ionic pairs, molecular sizes, and mobility and effects rising from the availability and cavity sizes distributions in pyridinium-based ionic liquids.

Physicochemical Characterization of n-Butyl-3-methylpyridinium Dicyanamide Ionic Liquid

The room temperature ionic liquid n-butyl-3-methylpyridinium dicyanamide has been characterized. Physicochemical properties such as density, speed of sound, refractive index, surface tension, and kinematic viscosity of the studied liquid have been experimentally measured in a wide range of temperatures. From results, coefficients of thermal expansion, molar refractions, dynamic viscosities and entropies and enthalpies of surface formation per unit surface area at the studied temperatures have been derived. We have analyzed the achieved results for evaluating the effect of the anionic structure in these properties, getting interesting results which lead us to a better understanding of the behavior of the ions in the fluids. Moreover, thermal properties of several pyridinium-based ionic liquids have been investigated. Finally, from both dynamic viscosity values and glass transition temperature of the studied liquids, a detailed analysis of the behavior in fragility terms has been performed.

Thermophysical study of 1-butyl-2-methylpyridinium tetrafluoroborate ionic liquid.

A thermophysical study of 1-butyl-2-methylpyridinium tetrafluoroborate in a wide range of temperatures has been performed. Thus, density, speed of sound, refractive index, kinematic viscosity, surface tension, and thermal properties have been measured, whereas coefficients of thermal expansion, molar refractions, dynamic viscosities, and entropies and enthalpies of surface formation per unit surface area at the studied temperatures have been calculated. Experimental results have been compared with those obtained for 1-butyl-3-methylpyridinium tetrafluoroborate and 1-butyl-4-methylpyridinium tetrafluoroborate to analyze the effect of the positional isomeric cationic structure on properties. A systematic characterization leads to understand the behavior of such compounds, being a fundamental step to develop their potential as new solvents.

Phase equilibrium of liquid mixtures: experimental and modeled data using statistical associating fluid theory for potential of variable range approach.

A study of the phase equilibrium (experimental and modeled) of mixtures formed by a cyclic ether and haloalkanes has been derived. Experimental data for the isothermal vapor liquid equilibrium of mixtures formed by tetrahydrofuran and tetrahydropyran and isomeric chlorobutanes at temperatures of 298.15, 313.15, and 328.15 K are presented. Experimental results have been discussed in terms of both molecular characteristics of pure compounds and potential intermolecular interaction between them using thermodynamic information of the mixtures obtained earlier. The statistical associating fluid theory for potential of variable range (SAFT-VR) approach together with standard combining rules without adjustable parameters has been used to model the phase equilibrium. Good agreement between experiment and the prediction is found with such a model. Mean absolute deviations for pressures are of the order of 1 kPa, while less than 0.013 mole fraction for vapor phase compositions. In order to improve the results obtained, a new modeling has been carried out by introducing a unique transferable parameter k(ij), which modifies the strength of the dispersion interaction between unlike components in the mixtures, and is valid for all the studied mixtures being not temperature or pressure dependent. This parameter together with the SAFT-VR approach provides a description of the vapor-liquid equilibrium of the mixtures that is in excellent agreement with the experimental data for most cases. The absolute deviations are of the order of 0.005 mole fraction for vapor phase compositions and less than 0.3 kPa for pressure, excepting for mixtures containing 2-chloro-2-methylpropane which deviations for pressure are larger. Results obtained in this work in the modeling of the phase equilibrium with the SAFT-VR equation of state have been compared to the ones obtained in a previous study when the approach was used to model similar mixtures with clear differences in the thermodynamic behavior. We show how the SAFT-VR approach is capable of differentiating the molecular features of a relatively wide set of different mixtures.

Optical and diffractive studies of pyridinium-based ionic liquids

Electronic absorption, steady-state fluorescence spectra and X-ray diffraction patterns for several pyridinium-based ionic liquids (ILs) (1-butyl-3-methylpyridinium tetrafluoroborate, 1-butyl-4-methylpyridinium tetrafluoroborate, 1-octyl-3-methylpyridinium tetrafluoroborate and 1-butyl-3-methylpyridinium dicyanamide) have been obtained. A systematic study has been performed for different ILs in terms of structural characteristics obtaining remarkable results. The present characterisation, centre of attention in theoretical and practical fields, leads to understand the complex behaviour of such compounds and is an essential step for their potential development as new solvents in extended applications.

Temperature dependence of surface tension of 2-methyl-1-propanol and 2-methyl-2-propanol+n-hexane mixtures

Surface tensions of binary mixtures of 2-methyl-1-propanol or 2-methyl-2-propanol with n-hexane have been measured in the temperature range 283.15 K–313.15 K for mixtures containing 2-methyl-1-propanol and from 298.15 K to 313.15 K for mixtures formed by 2-methyl-2-propanol, with a drop volume tensiometer. The corresponding surface tension deviations have been calculated and correlated. Using the temperature dependence of surface tensions, the entropy and enthalpy of surface formation per unit area were evaluated at the studied temperatures.

Refractive indices and molar refractions of binary mixtures formed by some cyclic ethers and isomeric chlorobutanes

Refractive indices of binary mixtures formed by a cyclic ether (tetrahydrofuran or tetrahydropyran) and each of the isomeric chlorobutanes (1-chlorobutane, 2-chlorobutane, 1-chloro-2-methylpropane and 2-chloro-2-methylpropane) have been measured at two temperatures, 298.15 K and 313.15 K. From experimental data, refractive index deviations and molar refractions have been calculated. Furthermore, several common mixing rules have been used to predict refractive indices of the mixtures from their experimental densities reported previously.