Oxidative Desulfurization of Diesel Oil Using Mesoporous Phosphotungstic Acid/SiO2 as Catalyst

Ordered mesoporous phosphotungstic acid/SiO₂ (HPW/SiO₂) with Keggin‐type heteropolyacids (HPAs) encapsulated into a SiO₂ framework has been synthesized and used as the catalyst for oxidative desulfurization of diesel fuel. The sulfur compounds in diesel were oxidized and removed at a temperature range of 50–80 °C with H₂O₂ as the oxidant and acetonitrile as the extraction agent. The sulfur content in diesel was reduced to as low as 48–86 μg/g from the initial level of 438 μg/g. The loss in catalytic activity was negligible even after five cycles of use, and the reduction of the sulfur content was enhanced with increasing the immobilized phosphotungstic acid (HPW) concentration. Oxidation of model compounds showed that in the heterogeneous system both the electron density and the steric hindrance affected the reactivity of these sulfur compounds. The reactivities of these sulfur compounds studied in this work followed the order of dibenzothiophene > 4,6‐dimethydibenzothiophene > benzothiophene.