Contents lists available at ScienceDirect Separation and Purification Technology journal homepage: www.elsevier.com/locate/seppur Experimental screening towards developing ionic liquid-based extractive distillation in the dearomatization of refinery streams Pablo Navarro a,b , Marcos Larriba a , Noemí Delgado-Mellado a , Miguel Ayuso a , Marta Romero a , Julián García a, ⁎ , Francisco Rodríguez a a Department of Chemical Engineering, Complutense University of Madrid, E–28040 Madrid, Spain b CICECO – Aveiro Institute of Materials, Department of Chemistry, University of Aveiro, Aveiro, Portugal ARTICLE INFO Keywords: Ionic liquids Aromatic/aliphatic separation Vapor-liquid-liquid equilibrium Extractive distillation ABSTRACT Ionic liquids (ILs) are potential neoteric solvents to design new advanced separation processes. Among several separation cases studied so far, the good performance of ILs regarding the dearomatization of liquid fuels, i.e. pyrolysis and reformer gasolines, has received especially attention. Indeed, a wide number of works has been done to characterize the phase equilibria for {aliphatic + aromatic + ILs} systems as well as the IL thermo- physical properties, concluding in the development of a liquid-liquid extraction process. However, this tech- nology seems not to be enough to fulfill current aromatic commercial standards nor potential incoming re- strictions for aromatic content in liquid fuels as a result of its low separation effectiveness for extreme aliphatic and aromatic purification. Extractive distillation with ILs stands as a new process configuration to overcome these limitations by enhancing the aliphatic/aromatic relative volatilities. In this work, an IL experimental screening in the n-heptane/toluene separation was done to further develop this new IL-based technology. Nine ILs were tested as mass agents in a wide range of conditions, i.e. solvent to feed (S/F) ratios from 1 to 10 and temperatures from 323.2 to 403.2 K. The required vapor-liquid-liquid equilibria (VLLE) data were obtained by an experimental procedure based on headspace gas chromatography (HS-GC) developed in the framework of this work. Although all pre-selected ILs have shown good performance, tricyanomethanide-based ILs have been the most promising mass agents. 1. Introduction ILs are non-conventional salts that are liquid under 373 K and have negligible vapor pressure, showing an interesting liquid range of use [1]. Among other purposes, ILs have been successfully used in a high number of separation cases as solvents in liquid-liquid extraction pro- cesses or as mass agents in vapor-liquid separation technologies [2–11]. Liquid-liquid extraction processes using ILs have been designed to eliminate non-desirable compounds in final streams (i.e. aromatics or drugs) or to recover high-valuable substances (i.e. metals, proteins, nucleic acids, lipids or amino-acids) from waste streams [12–18]. As mass agents, ILs have been mainly proved in homogeneous {al- cohol + water + IL} systems [19–22]. Focusing the attention in the dearomatization of hydrocarbon streams, which is one of the most prolific and hopeful research lines using ILs [23], several remarks can be given from the wide majority of the published works until now. It is important to mention that all these works were aimed in designing a liquid-liquid extraction process with ILs. From the liquid-liquid equilibrium (LLE) data referring to {ali- phatics + aromatics + ILs} systems, it is possible to highlight the suit- ability of cyano-based and bis(trifluoromethylsulfonyl)imide-based ILs as can be seen in the recent review on the aromatic/aliphatic separation topic by Canales and Brennecke or in previous works based on both experimental data or COSMO-RS prediction studies [23–26]. Thiocya- nate-based and dicyanamide-based ILs have shown aromatic/aliphatic selectivities quite higher than those for conventional organic solvents [27–29], whereas tricyanomethanide-based and bis(tri- fluoromethylsulfonyl)imide-based ILs displayed comparable or even higher aromatic distribution ratios in mass basis in comparison with those exhibited by the conventional solvents such as sulfolane [26,27,30]. In addition to this, all of these ILs present low viscosities and enough densities to ensure two liquid phases splitting [26]. Therefore, by using these pure ILs or a well-selected binary mixture of them in the aromatic extraction from aromatic main sources, i.e. pyr- olysis and reformer gasolines, the extractor efficiencies and size would be similar to that in the Sulfolane process and the aromatic purity in the https://doi.org/10.1016/j.seppur.2018.03.024 Received 23 January 2018; Received in revised form 12 March 2018; Accepted 12 March 2018 ⁎ Corresponding author. E-mail address: jgarcia@quim.ucm.es (J. García). Separation and Purification Technology 201 (2018) 268–275 Available online 14 March 2018 1383-5866/ © 2018 Elsevier B.V. All rights reserved. T