Five-and six-membered heteroaromatic nitrogen compounds play an inhibiting role in the hydrodesulfurization of diesel oil. In this work, the ionic liquids (ILs) are used as green solvents to remove such compounds by liquid-liquid extraction (LLE). Approximately 168 ILs comprising cations which include 1-ethyl-3methylimidaozlium [EMIM], 1-ethylpyridinium [EPY], 1-ethyl-1-methyl pyrrolidinium [EPYRO], 1-ethyl-1-methylpiperidinium [EMPIP], 4-ethyl-4-methyl morpholinium [EMMOR], and 1,2,4-trimethylpyrazolium[TMPYZO] combined with 26 anions were investigated in this work. The infinite dilution activity coefficient (IDAC) was predicted through the conductor-like screening model for real solvents (COSMO-RS) model in order to screen the potential solvents. Initially the model was benchmarked via IDAC and LLE predictions. LLE was predicted for four reported ternary systems in which a nitrogen heterocycle was one of the compounds. The average root-mean-square deviation (rmsd) obtained was 10%. The IDAC values were predicted for pyridine in two ionic liquids, namely [BMIM][BF 4 ] and [EMIM][TOS], with a root-mean-square (rms) error of 8%. Thereafter the selectivity, capacity, and performance index at infinite dilution were calculated to evaluate the performance. It was found that the five-membered nitrogen species having high delocalized electron density possessed 3 orders of magnitude higher selectivity than the six-membered nitrogen species. For the fivemembered ring structures, the selectivity was found to follow the orderFor the six-membered heterocycle, it followed the order [EPY] >Irrespective of nitrogen heterocycle, anions such as thiocyanate [SCN] and acetate [Ac] gave high values of selectivity. In general cations without aromatic rings such as [EPYRO], [EMPIP], and [EMMOR] gave higher selectivity and capacity irrespective of the nitrogen heterocycle.

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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.

[BF 4 ]. An inverse relation was observed between the activity coefficient at infinite dilution predicted via COSMO-RS-based model and interaction energies. The dominance of CH-p interaction was evident from the sigma profiles of ionic liquid together with thiophene and pyridine.

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