Thermodynamic modelling of liquid-liquid extraction of naphthenic acid from dodecane using imidazolium based phenolate ionic liquids Syed Nasir Shah a, ⁎, M.I. Abdul Mutalib d , M. Farid Ismail b , Humbul Suleman d , Kallidanthiyil Chellappan Lethesh a,c , Rashidah Binti Mohd Pilus e a Centre of Research in Ionic Liquids, Universiti Teknologi Petronas, Bandar Seri Iskandar 32610, Perak, Malaysia b Department of Chemistry, Universiti Putra Malaysia, 4330 Serdang, Malaysia c Center for Biofuel and Biochemical Research, Universiti Teknologi Petronas, Bandar Seri Iskandar 32610, Perak, Malaysia d Department of Chemical Engineering, Universiti Teknologi Petronas, Bandar Seri Iskandar 32610, Perak, Malaysia e Department of Petroleum Engineering, Universiti Teknologi Petronas, Bandar Seri Iskandar 32610, Perak, Malaysia abstract article info Article history: Received 14 September 2015 Accepted 18 March 2016 Available online xxxx In this work, N-alkyl imidazolium based ionic liquids with phenolate anions have been used for the separation of naphthenic acid from model oil. The liquid-liquid equilibrium (LLE) data for the ternary mixture of [C n mim][Phe], dodecane and naphthenic acid were experimentally obtained at a constant temperature of 303.15 K and atmo- spheric pressure. The effect of chain length on the extraction capability was observed by calculating the distribu- tion coefficient. The experimental tie line data was correlated using the non-random two liquid model (NRTL) and Universal Quasi Chemical (UNIQUAC) model and new interaction parameters for the ternary systems are re- ported. The experimental data provides a good correlation with the modelling data and a very low root mean square deviation (RMSD) value was observed for all the systems. © 2016 Elsevier B.V. All rights reserved. Keywords: Ionic liquids (ILs) Naphthenic acid (NA) Phenolate anion (Phe) Alkyl methyl imidazole Liquid-liquid equilibrium (LLE) Non-random two liquid model (NRTL) Universal Quasi Chemical (UNIQUAC) 1. Introduction Ionic liquids (ILs) being designer solvents have found a large number of applications in academia as well as in the industry. The properties like negligible vapour pressure, high thermal and chemi- cal stability, non-flammability; high heat capacity, high ionic con- ductivity etc. make them a greener choice for a range of industrial applications. In addition, ILs exhibit a very good solubility for organic compounds thus making them an excellent solvent for liquid-liquid extraction process [1,2]. These desirable properties make them suit- able in numerous applications in which many conventional solvents are non-applicable and in-effective. Liquid-liquid extraction has found large applications in the separation industry because of the mild process conditions applied during the process i.e. low temperature and pressure. The solvent to be used in liquid-liquid extraction should have a high selectivity towards the solute. Moreover, it should be eco- nomical to produce, recyclable, and robust to withstand various pro- cessing environments. Most of the organic solvents are carcinogenic, highly volatile and their recyclability is very low. Contrarily, most of the ILs are greener, non-volatile and highly recyclable [3–6]. But the core issue that stands in the way of commercialisation is the high cost of ILs. However, in one of the recent modelling and simulation studies on the ILs production process shows that ILs can be produced at lower cost ( $1.24 kg -1 ), which is in comparison with most of the organic sol- vents such as acetone or ethyl acetate with a cost of $1.30–$1.40 kg -1 [7].Similarly, in another study, the extraction of aromatic hydrocarbon from aliphatic hydrocarbon with 4-methyl-N-butylpyridinium tetraflu- oroborate was modeled using ASPEN resulting in a positive margin of about € 20 million per year [8]. These results indicate that ILs are not necessarily expensive, and therefore large-scale ILs-based processes can become a commercial reality. Naphthenic acid removal from acidic crude is one of the major concerns of refiners all over the world. Naph- thenic acid presence in heavy crude can cause corrosion in the refinery equipment and storage tanks. Additionally, it affects the combustion characteristic of the finished products [9,10]. Thus the removal of naph- thenic acid from crude oil is highly desirable. On the other hand, naph- thenic acids have a very complicated moieties and a wide variety of compounds lie in the definition of naphthenic acid. Naphthenic acids can be defined as a mixture of cyclic, aromatic and linear monocarbox- ylic acids present in the crude oil with the general formula C n H 2n +z O 2 , where n indicates the number of carbon atoms, z indicates the deficien- cy of hydrogen because of the presence cyclic or aromatic groups. The value of z can be a negative integer or zero [11–14]. Commercial naph- thenic acid is obtained from jet fuel, kerosene and diesel fractions by caustic wash followed by acidification of caustic stream with sulfuric Journal of Molecular Liquids 219 (2016) 513–525 ⁎ Corresponding author. E-mail address: nasir876@gmail.com (S.N. Shah). http://dx.doi.org/10.1016/j.molliq.2016.03.053 0167-7322/© 2016 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Journal of Molecular Liquids journal homepage: www.elsevier.com/locate/molliq