Green Fuel Desulfurization with β‑Cyclodextrin Aqueous Solution for Thiophenic Sulfides by Molecular Inclusion

Achieving green fuel desulfurization for thiophenic sulfides (TpSs) is a very urgent theme for the production of clean oil. Herein, an aqueous solution of β-cyclodextrin (βCD) as a novel desulfurization agent that is environmentally friendly and low cost was approached in the inclusion removal of the TpSs in fuel. It was found that βCD aqueous solution (βCD aq) has high selectivity to remove the TpSs in fuel. The desulfurization conditions of the molecular inclusion with βCD aq are significantly more moderate than those of the existing desulfurization methods. Room temperature is suitable for βCD aq to remove the three TpSs. The removal efficiency of the three TpSs using βCD aq was in the order of benzothiophene (56.71%) > dibenzothiophene (51.86%) > thiophene (45.38%) when the temperature was 30 °C and the volume ratio of βCD aq to n-heptane containing 0.1 mg·g–1 sulfur was 2:1. The inclusion ratio of βCD and TpS in the formed inclusion complex is 1:1 for all three TpS’s, and the TpS can easily enter the cavity of βCD from its wide end. A reasonable desulfurization mechanism through the molecular inclusion of βCD in aqueous solution was proposed based on the experimental and computational results. This study indicates that βCD aq could be developed into a green desulfurization method for the removal of TpSs via molecular inclusion.