Deep Desulfurization of Fuel Diesels Using Alkyl Sulfate and Nitrate Containing Imidazolium as Ionic Liquids

Abstract

1-ethyl-3-methylimidazolium ethyl sulfate [Etmim][EtSO4 ],1, 3-dimethylimidazolium methyl sulfate [Mmim][MeSO4 ] and 1-octyl-3-methylimidazolium nitrate [Omim][NO3 ] ionic liquids have been used in thermal oxidative desulfurization of model fuel oils consisting of 500 ppm solutions of benzothiophene (BT) and dibenzothiophene (DBT) in dodecane. The efficiency of sulfur removal from BT and DBT solutions by these ILs as well as the effect of anion and cation chain length have also been investigated. The ILs studied performed pretty efficiently in removal of sulfur containing compounds and sulfur contents have been reduced to 18-27% following the order below: [Mmim][MeSO4 ] > [Etmim][EtSO4 ] > [Omim][NO3 ]. To further study the performance of the ILs studied, multiple extractions of BT and DBT solutions were also carried out to reduce sulfur content to 81% and 68% for DBT and BT solutions, respectively, after 5 extraction cycles. These environmentally friendly ILs could also be quantitatively regenerated and were shown to be as efficient in sulfur removal after 5 regeneration cycles.