Toward Application of Ionic Liquids to Desulfurization of Fuels: A Review

Over the past decades, the desulfurization of fuel oils has been known as one of the most challenging processes in petroleum refineries due to economic considerations. The presence of sulfur compounds results in SOx emissions, detrimentally affecting the equipment of refineries, the environment, and human health. In this direction, the unique features of ionic liquids have introduced them as a beneficial alternative for conventional desulfurization of fuel oils using traditional organic solvents. In this review, we aim to study ionic liquids used in different desulfurization processes of fuel oils, including hydrodesulfurization (HDS), oxidative desulfurization (ODS), extractive desulfurization (EDS), extraction combined with oxidation desulfurization (EODS), extractive and catalytic oxidative desulfurization (ECODS), and liquid–liquid extraction (LLE). Furthermore, governing factors, including temperature, mixing time, reusability of ionic liquids, stirring speed, sulfur structure nature, and molar and mass ratios of oxidants, ionic liquids, and catalysts, have been reviewed in detail.