Evaluation of the solvent structural effect upon the vapor eliquid equilibrium of [C 4 C 1 im][Cl] þ alcohols Naima Chouireb a, b , Imran Khan c , Emanuel A. Crespo b , Mariana B. Oliveira b , F  elix Llovell d , Lourdes F. Vega e , O. Tafat-Igoudjilene a , A. Ait Kaci a , Luís M.N.B.F. Santos f , Pedro J. Carvalho b, * , Jo ~ ao A.P. Coutinho b a Laboratory of Thermodynamic and Molecular Modeling, Faculty of Chemistry, USTHB, BP 32, El-Alia, Bab-Ezzouar, Algies, Algeria b CICECO e Aveiro Institute of Materials, Departement of Chemistry, University of Aveiro, 3810-193 Aveiro, Portugal c Department of Chemistry, College of Science, Sultan Qaboos University, PO Box 36, PC 123, Muscat, Oman d IQS School of Engineering, Department of Chemical Engineering and Materials Science, Universitat Ramon Llull, Via Augusta, 390, 08017 Barcelona, Spain e Gas Research Center and Chemical Engineering Department, The Petroleum Institute, P.O. Box 2533, Abu Dhabi, United Arabs Emirates f Centro de Investigaç~ ao em Química, Departamento de Química e Bioquímica, Faculdade de Ci^ encias da Universidade do Porto, R. Campo Alegre 687, P- 4169-007 Porto, Portugal article info Article history: Received 19 December 2016 Received in revised form 23 February 2017 Accepted 24 February 2017 Available online 27 February 2017 Keywords: Vapor-liquid equilibrium 1-Butyl-3-methylimidazolium chloride Alcohols Isomers Soft eSAFT Activity coefficients Binary mixtures Alkyl chain length abstract A systematic isobaric vapor-liquid equilibrium (VLE) study of seven binary mixtures of 1-butyl-3- methylimidazolium chloride, [C 4 C 1 im][Cl], and methanol, propan-1-ol, propan-2-ol, butan-1-ol, butan- 2-ol, tert-butanol (2-methylpropan-2-ol), iso-butanol (2-methylpropan-1-ol) and pentan-1-ol, was car- ried out at three different system pressures (0.1, 0.07 and 0.05 MPa). Activity coefficients were estimated from the boiling temperatures of the binary mixtures. soft-SAFT equation of state was used to describe the experimental VLE data and all together, allowed to infer and understand the effect of the alcohol alkyl chain length and structural isomerism on the molecular interactions between the IL and the alcohols. © 2017 Elsevier B.V. All rights reserved. 1. Introduction Vapor-liquid equilibrium (VLE) data for azeotropic or close- boiling systems are crucial for better understanding the thermo- dynamic behavior and design of separation processes [1]. The separation of azeotropic mixtures has conventionally been one of the most challenging tasks in industrial processes since simple distillation stood unfeasible. Several other separation processes suitable for azeotrope mixtures separation, like extractive distilla- tion, pressure swing distillation, liquid-liquid extraction and adsorption membranes, have been developed. Among them, extractive distillation is the most widely used for azeotrope separation. Based on the addition of a third solvent with a high boiling point, i.e. entrainer, the system relative volatility is modified promoting the separation [1]. Organic solvents [2], inorganic salts [3], hyper-branched polymers [4] or dendrimers [5] have been investigated as feasible entrainers. Recently, ionic liquids (ILs), a novel class of solvents, have attracted an increased interest as en- trainers for extractive distillation [1e6]. The use of ILs can stand as a technologically and environmen- tally favorable alternative to traditional entrainers in separation of organic substances. ILs have received a continuous attention in the past years as solvents with enhanced potential and feasible sol- vents to replace volatile organic solvents, mainly due to their exceptional physical and chemical properties. They are organic salts whose organic cation and inorganic or organic anion asymmetry and/or charge dispersion allows them to remain liquid at temper- atures below 373 K. The cation and the anion can be selected and * Corresponding author. E-mail address: quijorge@ua.pt (P.J. Carvalho). Contents lists available at ScienceDirect Fluid Phase Equilibria journal homepage: www.elsevier.com/locate/fluid http://dx.doi.org/10.1016/j.fluid.2017.02.016 0378-3812/© 2017 Elsevier B.V. All rights reserved. Fluid Phase Equilibria 440 (2017) 36e44