Ionic liquids for the removal of sulfur and nitrogen compounds in fuels: a review

Air pollution is partly due to the emission of toxic sulfur and nitrogen oxides during fuel combustion. Therefore, these compounds should be removed from fuels. For that, ionic liquids have been recently developed to extract sulfur and nitrogen compounds from petroleum and fuels. Ionic liquids can extract S- and N-containing compounds either simultaneously or selectively. Ionic liquids usage appears better than classical desulfurization and denitrogenation processes due to the efficiency and selectivity of ionic liquids. Here we review methods for desulfurization and denitrogenation with focus on extraction by ionic liquids, and their regeneration and recycling. We also discuss limitations of ionic liquids, such as environmental biodegradation, bioaccumulation and corrosivity.