Extraction desulfurization of fuels with ‘metal ions’ based deep eutectic solvents (MDESs)

Abstract

Organic sulfides in fuels have become one of the main sources of air pollution and as a result, deep desulfurization of fuels has become a hot issue. A deep eutectic solvent (DES) has provided a new route for the deep extraction desulfurization of fuels, based on its cheap and easily obtained raw materials, high desulfurization efficiencies and environmentally friendly properties. In this study, a series of three-component ‘metal ions’ based deep eutectic solvents (MDESs) was designed and synthesized. The extraction desulfurization performance of these MDESs was investigated and the process was optimized. Compared to traditional existing DESs, the extraction efficiency of these MDESs was higher. TBAC : PEG : FeCl₃ (4 : 1 : 0.05) achieved the highest desulfurization efficiency, which could reach up to 89.53% for one cycle. Deep desulfurization was realized after only two extraction cycles. The optimization of the extraction desulfurization process showed that the extraction equilibrium can be reached within 15 min at room temperature. Moreover, the recycling of TBAC : PEG : FeCl₃ was realized successfully by washing with ether. Research on the mechanism showed that apart from the hydrogen bonding interactions, metal ions in MDESs also act as coordination compounds, which results in higher desulfurization efficiencies. This research provides an effective technology for removing sulfides from fuels.