Insight into the mechanism of tuned extractive desulfurization by aqueous tetrabutylphosphonium bromide

Molecular dynamics simulations with the combination of FT-IR and 1H NMR spectra were carried out to study the mechanism of tuned extractive desulfurization by aqueous tetrabutylphosphonium bromide (TBPB). The intermolecular interaction and microstructure of TBPB with water and the sulfur compound dibenzothiophene (DBT) were investigated. Both the spectra and MD simulation results indicated that TBPB with a small amount of water has strong CH–π interaction between TBP+ cation and dibenzothiophene (DBT) and hydrogen bonding between Br− anion and DBT, which are the driving forces for extraction of DBT into aqueous TBPB phase in fuel desulfurization. Further addition of water into aqueous TBPB phase causes the solvation of cation and anion, which weakens the interactions of TBPB with DBT and hence facilitates DBT aggregation and TBPB recovery. The results provide an insight into the mechanism of water tuned extraction and regeneration process in fuel desulfurization.