Phase equilibria of toluene/heptane with deep eutectic solvents based on ethyltriphenylphosphonium iodide for the potential use in the separation of aromatics from naphtha

Mukhtar A. Kareem, Farouq S. Mjalli, Mohd Ali Hashim, Mohamed K O Hadj-Kali, Fatemeh Saadat Ghareh Bagh, Inas M. Alnashef

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In this work, the liquid-liquid extraction of toluene from hydrocarbons mixtures (toluene/heptane) was investigated using deep eutectic solvents as solvents. Ethyltriphenylphosphonium iodide as a salt with either ethylene glycol or sulfolane as hydrogen-bond donors (HBDs) were utilized for synthesizing six DESs. (Liquid + liquid) equilibria data were determined experimentally for the ternary system (toluene + heptane + DES) at (30, 40, 50, and 60) C and atmospheric pressure. Hand correlation was applied to establish the reliability of the experimental data. In many cases the correlation factor is found close to unity which indicates high reliability of the data. The selectivities and distribution coefficients were used to determine the suitability of these DESs as solvents for this extraction process. Higher selectivities than those published for sulfolane as a commercial solvent were observed. The DES made from ethyltriphenylphosphonium iodide and sulfolane at salt:HBD of 1:4 showed the best separation capability at 30 C. Thus, it was further characterized by measuring its viscosity and refractive index at a range of temperatures to help understand its physical behaviour needed for process design. The non-random two-liquid (NRTL) model was applied successfully to correlate the experimental tie-lines and to calculate the phase compositions of the ternary systems. It has been found that the third non-randomness parameter varies linearly with the HBD number of moles.

Original languageEnglish
Pages (from-to)138-149
Number of pages12
JournalJournal of Chemical Thermodynamics
Publication statusPublished - 2013



  • Aromatics separation
  • Deep eutectic solvents
  • Ionic liquids analogues
  • Liquid-liquid extraction
  • Phosphonium salts

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Atomic and Molecular Physics, and Optics
  • Materials Science(all)

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