Article pubs.acs.org/jced
Activity and Osmotic Coefficients of Binary Mixtures of NTf2− Ionic Liquids with a Primary Alcohol Noelia Calvar,† Á ngeles Domínguez,‡ and Eugénia A. Macedo*,† †
LSRE-Laboratory of Separation and Reaction Engineering, Associate Laboratory LSRE/LCM, Department of Chemical Engineering, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, s/n, Porto 4200-465, Portugal ‡ Advanced Separation Processes Group, Department of Chemical Engineering, University of Vigo, Campus Lagoas-Marcosende, 36310 Vigo, Spain S Supporting Information *
ABSTRACT: The vapor pressure osmometry technique (VPO) was used in this study to determine the osmotic and activity coefficients of several mixtures which contain 1-propanol and an equimolar mixture of two ionic liquids at T = 323.15 K. The equimolar mixture of ionic liquids is formed by 1-alkyl-3-methylimidazolium and/or 1-alkyl-3methylpyridinium-based ionic liquids with bis(trifluoromethylsulfonyl)imide as anion. A comparison between the results obtained in this work and those for mixtures with the same alcohol and the corresponding pure ionic liquids forming the equimolar mixture was carried out so the effect that mixing two ionic liquids can have on the osmotic and activity coefficients and vapor depression of the solvent can be analyzed. The Pitzer model for mixed electrolytes has been applied to represent the experimental data, and the standard relative deviations obtained between the calculated and experimental osmotic coefficients were found to be less than 0.075.
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INTRODUCTION During the past decade, many studies have been carried out on ionic liquids (ILs), including the properties of pure ionic liquids as well as of their binary mixtures mainly with organic solvents. Lately, binary mixtures formed by two ionic liquids are drawing attention, since the combination of ionic liquids can improve target properties and extend their applicability range. In this context, binary mixtures of ILs have been studied for liquid− liquid extraction,1,2 as solvents for chemical synthesis3,4 and especially for electrochemical applications.5−9 The studied properties include density,7,8,10−15 viscosity,6,8,10,11,13−16 and conductivity,9,11,13,17−19 where the excess properties obtained are generally small, showing the almost ideal mixing behavior of these properties. Several studies on the thermal behavior of mixtures of two ILs have been also carried out.5,8,9,13,14,17,20−24 Although there are works where mixtures of one pure IL and a solvent are used in vapor pressure osmometry (VPO) studies, no works where mixtures formed by binary mixtures of ILs and a solvent are studied have been found in the literature. In order to analyze the influence of the presence of mixtures of ionic liquids on their interactions in mixtures with an alcohol, the VPO technique was employed to measure osmotic and activity coefficients and vapor pressures of systems containing the primary alcohol 1-propanol and an equimolar mixture of two ionic liquids with the same anion. The studied mixtures are 1-propanol + 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide/1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide and 1-ethyl-3-methylimidazolium © XXXX American Chemical Society
bis(trifluoromethylsulfonyl)imide/1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide and 1-ethyl-3-methylpyridinium bis(trifluoromethylsulfonyl)imide/1-butyl-3-methylpyridinium bis(trifluoromethylsulfonyl)imide and 1-ethyl-3-methylpyridinum bis(trifluoromethylsulfonyl)imide/1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (1-propanol + [EMim][NTf2]/ [HMim][NTf2] and [EMim][NTf2]/[BMim][NTf2] and [EMpy][NTf2]/[BMpy][NTf2] and [EMpy][NTf2]/[HMim][NTf2]). The results obtained are compared with the behavior of the mixtures containing the corresponding pure ionic liquids forming the equimolar mixture; furthermore, the selection of an equimolar mixture of ILs allows comparison of the results with its corresponding intermediate pure component, i.e., the ionic liquid whose alkyl side chain length is intermediary between the alkyl side chain lengths of the two ILs of the equimolar mixture. The Pitzer model for mixed electrolytes25 was used for the correlation and prediction of the experimental osmotic coefficients.
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EXPERIMENTAL SECTION Chemicals. All of the ionic liquids involved in this study were purchased from Iolitec GmbH (Heilbronn, Germany). All of Special Issue: Proceedings of PPEPPD 2016 Received: June 30, 2016 Accepted: October 25, 2016
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DOI: 10.1021/acs.jced.6b00556 J. Chem. Eng. Data XXXX, XXX, XXX−XXX
Journal of Chemical & Engineering Data
Article
Table 1. Purity, Water Content, and Supplier of the Pure Compounds compound
purity in mass fraction
water content/ppm
supplier
purification method
[EMim][NTf2] [BMim][NTf2] [HMim][NTf2] [EMpy][NTf2] [BMpy][NTf2] 1-propanol
≥0.99 ≥0.99 ≥0.99 ≥0.99 ≥0.97 ≥0.999
