Mechanism of extractive/oxidative desulfurization using the ionic liquid inimidazole acetate: a computational study.

The dual role of the ionic liquid 1-butyl-3-methyl-imidazolium trifluoroacetic acid ([Cmim]TFA) as an extractant for thiophene (TH) and a catalyst for the oxidation of TH was explored at the molecular level by performing density functional theory (DFT) calculations. The calculated interaction energies demonstrated why [Cmim]TFA is a better extractant for thiophene sulfone (THO) than for TH. Two pathways were proposed for the oxidation of TH to THO with [Cmim]TFA acting as a catalyst. In the dominant pathway, a peracid is formed which then oxidizes TH to the sulfoxide and sulfones. The presence of [Cmim]TFA was found to greatly reduce the barrier to the oxidative desulfurization (ODS) of TH using HO as an oxidant. Graphical Abstract Possible reaction mechanisms of TH with the aid of [C4mim]TFAᅟ.