Removal of mercaptans from light oils using ionic liquid-NaOH aqueous solution as extractants

The application of ionic liquids as alternatives to conventional organic solvents in the extraction process has been investigated. In the present study, fourteen species of imidazolium-based ionic liquids were added into the NaOH (aq) to remove the mercaptans. The influences of anion species and cation alkyl chain length of the imidazolium-based ionic liquids on the performance of mercaptan removal from light oils have been discussed. The efficiency of extraction for mercaptans exhibited the order of [Ac]− > [OH]− ≈ [Br]− > [BF4]−. The longer alkyl chain imidazolium-based ionic liquids contributed to enhance desulfurization rate of 1-butyl mercaptan. 100% desulfurization rate of 1-butyl mercaptan was achieved by the anion of Ac− ionic liquids and NaOH (aq) at a volume ratio of 40:1 (V(oil):V(ionic liquid)) and a short equilibrium time within 10 min.