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Separation of aromatics from aliphatics is a challenging process because of the close range of their boiling points and the formation of several combinations of azeotropes. Until now, no feasible separation process is available for aromatic concentrations below 20 wt%. In this work, we have investigated the possibility of using a selected deep eutectic solvent (DES) for the liquid-liquid extraction of benzene, toluene, ethylbenzene and m-xylene (BTEX) aromatics. The DES used in this work was synthesized by combining tetrabutylammonium salt and sulfolane. Equilibrium data for the ternary system consisting of BTEX aromatics, n-octane and DES were measured at 25 C and atmospheric pressure. The results showed that the used DESs have comparable distribution ratios and selectivities to those of commercial solvents.In all tested systems, sulfolane was not present in the hydrocarbon layer. It was also found that the selectivity decreases with decreasing polarity of the aromatic compound. The Non-Random Two Liquid (NRTL) model was successfully used to correlate the experimental tie-lines and to calculate the phase compositions of the ternary systems. In addition, the performance of COSMO-RS to predict the ternary tie-lines for the studied systems was evaluated and the s-profiles were used to explain the interaction between the DES and the aromatic compounds.

A total of 94 deep eutectic solvents (DESs) based on different combinations of salt cation, anion, hydrogen-bond donor (HBD) and salt:HBD molar ratio are screened via the conductor-like screening model for real solvents for potential use in the extractive denitrification of diesel. Five nonbasic and six basic nitrogen compounds were included in this study. The activity coefficient at infinite dilution, γ ∞ , of each nitrogen compound in the DESs was predicted; and the values are used to screen the DESs on the basis of selectivity, capacity, and performance index at infinite dilution (S ∞ , C ∞ , and PI). The extraction of nitrogen compounds using DES is driven by hydrogen-bonding interaction. It was found that nonbasic compounds report higher S ∞ and C ∞ than basic compounds. Ammonium-based DESs give higher S ∞ but phosphonium-based DESs report higher C ∞ . DESs combined with Cl − anion give higher S ∞ , but those with Br − anion report higher C ∞ . DESs with alcohol-and amide-based HBDs give higher S ∞ but HBDs with carboxylic acid group report high C ∞ . Molar ratio has little effect toward S ∞ and C ∞ . DESs with high values of S ∞ generally have high PI.

This work investigates the use of deep eutectic solvents (DESs) to extract sulfur-based compounds from n-heptane as model diesel compounds. Four DESs were prepared by combining tetrabutylammonium bromide or methyltriphenylphosphonium bromide with ethylene glycol, triethylene glycol, or sulfolane. All DESs showed good ability to extract thiophene with the best extraction efficiency (35%) being observed for the sulfolane-based DES. The extraction efficiency can be further enhanced to reach 98% when five extraction cycles are performed. Moreover, the DESs were easily regenerated using rotary evaporation. In addition,1H NMR analysis is used to elucidate the extraction mechanism. Finally, the COSMO-RS model was used to predict the ternary tie lines for the studied systems and the NRTL model allowed, correlating the experimental data with an average root-mean-square deviation of <2% for all DESs. These models can be utilized for further simulation analysis of the extraction process.

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Ab initio method was applied to investigate the interaction between six heterocyclic nitrogen compounds with 18 ionic liquids. Important quantum chemical descriptors like orbital energy values, orbital energy gap, and global scalar properties including hardness, softness, electronegativity, and electrophilicity index were calculated for each individual species, ionic liquid complexes, and complexes of ionic liquid with heterocyclic nitrogen compounds. The effect of interaction energy and partial charge transfer were also investigated for the ion pair and their complexes. COSMO-RS model is used for qualitative screening of the ionic liquids via σ-profile and σ-potential. Comparison between experimental and COSMO-RS predicted ternary tie-lines were done to validate computational method; good agreement was achieved with average RMSD less than 5%. From the results, ILs based on aromatic ring cations combined with either [EtSO4] or [Ac] anion are recommended as solvent for extractive denitrification of liquid fuels, with [EPY][EtSO4] being the most favorable IL for removal of heterocyclic nitrogen compounds from liquid fuels at 298.15 K.