The pyridinium-based ionic liquids (ILs) N-butylpyridinium tetrafluoroborate ([BPy][BF 4 ]), N-hexylpyridinium tetrafluoroborate ([HPy][BF 4 ]), and N-octylpyridinium tetrafluoroborate ([OPy][BF 4 ]) were found to be effective for the selective removal of aromatic heterocyclic sulfur compounds from diesel at room temperature. The results suggested that the structure and size of the cation greatly affect the extractive performance of ILs. The extractive performance using pyridinium-based ILs followed the orderand for the IL, the sulfur removal selectivity of sulfur compounds followed the order thiophene (TS) < benzothiophene (BT) < dibenzothiophene (DBT) under the same conditions. The pyridinium-based ILs would not contaminate the diesel due to their insolubility. On the other hand, diesel has a certain solubility in pyridinium-based ILs, varying from 0.49 wt % for [BPy][BF 4 ] to 1.97 wt % for [OPy][BF 4 ]. According to the results, [HPy][BF 4 ] and [OPy][BF 4 ] might be used as promising solvents for the extractive desulfurization of diesel.

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3-Methylpyridinium-based ionic liquids (ILs) were demonstrated to be effective for the selective removal of aromatic heterocyclic sulfur compounds from diesel at room temperature. The results indicated that the extractive performance using 3-methylpyridinium-based ILs followed the order of 1-octyl-3-methylpyridinium tetrafluoroborate ([). For a given IL, the sulfur removal selectivity of sulfur compounds followed the order of dibenzothiophene (DBT) > benzothiophene (BT) > thiophene (TS) > 4,6dibenzothiophene (4,6-DMDBT) under the same conditions, except for [C 8 3 MPy][BF 4 ] IL, which followed the order of DBT > BT > 4,6-DMDBT > TS. The 3-methylpyridinium-based ILs are insoluble in diesel, while diesel has a certain solubility in 3-methylpyridinium-based ILs, with the content varying from 6.1 wt % for [C 4 3 MPy][BF 4 ] to 9.5 wt % for [C 8 3 MPy][BF 4 ]. The spent IL saturated sulfur compounds could be regenerated by a water dilution process. Considering these results, ILs studied in this work are more competitive and feasible for extractive desulfurization applications. Moreover, the extractive desulfurization using 3-methylpyridinium-based ILs could be used at least as a complementary process to hydrodesulfurization (HDS).