Roles of surface chemistry and structural defects of activated carbons in the oxidative desulfurization of benzothiophenes

• Acid-treated, wood-based activated carbon promotes benzothiophene oxidation.
• Effective materials possess high surface area and high density of surface acids.
• In situ formation of surface-bound percarboxylic acids is hypothesized.

A range of different activated carbons was characterized and evaluated for promotion of the oxidative desulfurization (ODS) of JP-8 fuel using H2O2 oxidant and acetic acid. Wood-based carbons activated by acid treatment showed much higher effectiveness than all other carbon types, regardless of source or activation method. Under identical test conditions designed to differentiate material performance, the most effective carbon material yielded 69% oxidation of 2,3-dimethylbenzothiophene (2,3-DMBT) whereas the ineffective materials scarcely out-performed the control (10% oxidation). To understand the characteristics most associated with reaction promotion, the textural, chemical, and defect features of the carbon materials were examined using a battery of techniques. The effective promoters all shared in common high surface areas and high pore volumes; however, surface area and pore volume alone could not explain the observed trends in performance. Investigating surface chemistry, presence of strong acid sites was strongly related to ODS performance. Overall, long-range order was not required for high activity, yet neither were edge defect sites. These results suggest that carbon promotes ODS by formation of percarboxylic acid species at defect sites within the carbon basal planes. Post-reaction analysis of the carbon materials provided evidence to support this explanation.