Extraction-adsorption coupled desulfurization of fuel oil by novel functionalized porous liquids

• A Novel Functionalized Porous liquid was successfully designed and synthesized. • A new way of extraction-adsorption coupled desulfurization is proposed. • The prepared PLs have stable structure under electrostatic interaction. • The PLs have excellent desulfurization performance even at high sulfur content. • The mechanism of the extraction-adsorption coupled desulfurization was proposed. Porous liquids (PLs) combine the advantages of porous solid materials and the fluidity of liquids, and show great potential for applications. Based on the interactions between sulfides in fuel oil and nitrogen-containing heterocyclic ionic liquid (ILs), dicationic imidazole-based ILs with different alkyl side chains and linkage chains, and benzyl-grafted DBU amidinocyclic IL were used as sterically hindered solvents to enhance the extractivity, and the microporous structure of metal-organic framework MIL-53(Al) improve the adsorption performance. Several novel functionalized PLs with dual roles of extraction and adsorption were synthesized under electrostatic interaction between the two. The results showed it had good extraction-adsorption coupled desulfurization performance of fuel oil. Under optimal conditions, the removal efficiencies reached to 67.67%, 85.5% and 84.34% for thiophene, benzothiophene and dibenzothiophene with initial sulfur concentration of 5000 ppm, respectively. Quantitative calculation and visualization analysis revealed the mechanism of desulfurization process, it is subject to the dual action of microporous structure and ILs. Due to the π-π stacking and van der Waals (VDW) forces between sulfides and ILs, thiophene-like sulfides is first extracted into the ILs phase, then diffuses to the two-phase interface between the ILs and MIL-53(Al), after screening by the window size, it enters into the pore and is firmly adsorbed under the effect of electrostatic interaction, Lewis acidic sites, π-π force, etc. The porous liquids provide a new direction for fuel desulfurization process, and is a new functionalized solvent with great application potential and research value.