Removal of dimethyl disulfide via extraction using imidazolium-based phosphoric ionic liquids

The imidazolium-based phosphoric ionic liquids, namely, N-methyl-N-methylimidazolium dimethyl phosphate ([Mmim]DMP), N-ethyl-N-methylimidazolium diethyl phosphate ([Emim]DEP) and N-butyl-N-methylimidazolium dibutyl phosphate ([Bmim]DBP), were prepared for removal of dimethyl disulfide (DMDS) from model oil through extractive desulfurization (EDS). The structures of the synthesized ionic liquids were systematically characterized and analyzed. Furthermore, the influences of various extraction parameters, for example, viscosities of ionic liquids, dosage and type of ionic liquids, reaction temperature, reaction time, and the reusability of ionic liquids, were studied. The experimental results showed that under the optimum extraction conditions the sulfur removal ability of the phosphoric ionic liquids followed the order of [Bmim]DBP ⩾ [Emim]DEP > [Mmim]DMP. It was also observed that the model oil was soluble in the ionic liquids, and the solubility of 12.9 mg(oil)/g(IL) was obtained for [Emim]DEP. In addition, the ionic liquids could easily be separated from the extraction mixture by simple decantation and could be reused at least five times after a reactivation treatment.