Screening method and mechanism of ionic liquid as extractant in fuel extraction desulfurization process

Abstract Background In the production of ultra‐low sulfur fuels, the use of extraction processes to remove sulfides from the fuel has various advantages. The selection of a suitable extractant is key to the extraction process. Ionic liquids (ILs) are known as green solvents and are designable, but there is a wide variety. In this study, an IL screening method was developed based on a conductor‐like screening model‐segment activity coefficient (COSMO‐SAC) model and a fuzzy comprehensive evaluation model. In addition, the feasibility of the method was verified by fuel extraction desulfurization experiments. Finally, the separation mechanism was explored through intermolecular interactions. Results In this study, suitable extractants were screened from 2400 ILs with 24 anions and 100 cation combinations. Based on the results of the fuzzy comprehensive evaluation model, five ILs were selected; 1‐hexyl‐3‐methylimidazolium hexafluorophosphate ([HMIM][PF 6 ]) was selected as the extractant and the single desulfurization rate could reach 72.74%. After four desulphurization experiments, the sulfur content in the model oil decreased from 1200 to 6.98 μg/g. The interaction energy difference between [HMIM][PF 6 ] + BT and [HMIM][PF 6 ] + OC ( ΔE = ‐12.8662 kJ·mol −1 ) is higher than those of the other four extractants. Conclusion The feasibility of the screened method was verified by the extraction desulfurization experiment. [HMIM][PF 6 ] was selected as the most suitable extractant. Furthermore, by analyzing the weak interaction between ILs and benzothiophene (BT) and n‐octane (OC), it was found that weak hydrogen bonds (HBs) and π–π interactions between [HMIM][PF 6 ] and BT play important roles in the extraction process. © 2022 Society of Chemical Industry (SCI).