Energy-efficient extractive desulfurization of gasoline by polyether-based ionic liquids

Abstract

A highly efficient extractive desulfurization (EDS) system with polyether-based ionic liquids (ILs) as extractants has been developed. The polyether ILs, with two PEG chains and a benzyl group, exhibit very high affinities for sulfur compounds, in particular, for benzothiophenes and phenyl sulfides. These exceptional affinities are due to various interactions between the IL and sulfur compounds, which include electrostatic effects, hydrogen bonding, π–π interactions, and so on. The extraction equilibrium can be achieved within a few minutes near room temperature. The desulfurization rates of the refractory sulfur compounds, viz. benzothiophene (BT), dibenzothiophene (DBT), and 4,6-dimethyldibenzothiophene (4,6-DMDBT), in model gasoline can reach 84.7%, 91.4%, and 81.0%, respectively. For multiple extractions of real gasolines, within four extraction cycles, the desulfurization rate of gasoline 93# was nearly 100%, while the desulfurization rates of gasoline 90# and light hydrocarbon gasoline reached 88.0% and 91.0%, respectively. Furthermore, the polyether IL stabilized by NaCl exhibited remarkable recyclability. The addition of NaCl into the IL minimized the loss of the extractant, making it negligible. After recycling the IL over 64 extraction cycles, the desulfurization rate was reduced by only a small amount and the mass loss of the IL was also very low (6.1%).