Deep oxidative extractive desulfurization of model diesel fuel using benzimidazolium based ionic liquid type gemini surfactants

Herein, the preparation of alkylated or arylated benzimidazolium ionic liquids type gemini surfactants (bimILs), and their application in diesel desulfurization is reported. The primary experiments exhibited that bimIL with a spacer linker composed of five methylene units was more effective than the one with two methylene units, so it was chosen for further investigation. To get bimILs that make different interactions with various S-compounds, bimILs with varying lipophilic tail (dodecyl or benzyl group), and accompanying anions (Cl − , Br − , NTf 2 − , PF 6 − and BF 4 − ) were prepared, and their chemical structure confirmed via FT-IR and 1 H NMR measurements. Then, a model diesel fuel was prepared using 500 ppm of thiophene (T), benzothiophene (BT), or dibenzothiophene (DBT) as aromatic S-compounds and subjected to desulfurization with the synthesized bimILs via the extractive desulfurization, and oxidative-extractive desulfurization techniques. The bimIL with benzyl group, NTf 2 − as an anion, and H 2 O 2 as oxidant has exhibited the highest efficiencies of 75.5% and 81.4% among the samples investigated in extractive desulfurization and oxidative-extractive desulfurization processes, respectively. These observed high efficiencies were attributed to the π-π interactions between the benzyl group of bimIL and aromatic rings of S-compounds (T, BT, and DBT). In experiments using the [2bbim-5][2FeCl 4 ] and [2bbim-5][FeCl 4 /FeCl 3 ], the efficiency increased to 86.6% and 91.5% at room temperature with a process time of 30 min, respectively.