Deep extractive desulfurization of dibenzothiophene with imidazolium or pyridinium-based ionic liquids

Four nitrate-based ionic liquids (ILs), i.e. 1-Butyl-3-methylimdazolium nitrate ([Bmim][NO3]), 1-Octyl-3-methylimdazolium nitrate ([Omim][NO3]), 1-Butylpyridinium nitrate ([BPy][NO3]), and 1-Octylpyridinium nitrate ([OPy][NO3]) were synthesized and used as extractant for the removal of dibenzothiophene (DBT) from the model oil. The effects of cation type, cation's alkyl chain length, extraction time, temperature, and IL/model oil volume ratio on the DBT removal were investigated. The ILs demonstrated high extraction performance with this order: [Omim][NO3] > [OPy][NO3] ≈ [Bmim][NO3] > ([BPy][NO3]. The results suggested that [Omim][NO3] could be utilized as an appropriate solvent for the extractive desulfurization of fuel oil. It could reduce 94.8% of sulfur content in model oil from 500 to 26 ppm at 25 °C and IL/model oil volume ratio of 1:1 in a single-stage extraction. [Omim][NO3] could be reused six times without an impressive decrease in its activity.