A microwave-ultrasound assisted synthesis of defective TiO2 and WO3/TiO2 nanoparticles for ultralow sulfur diesel production

•Novel synthesis of defective WO3/TiO2 nanoparticles via a microwave-ultrasound assisted method.•Quantitative determination of oxygen defects by Rietveld refinement method.•Ultralow sulfur diesel production via the oxidative desulfurization technique.•A well correlation of oxygen defects and surface Lewis acidity with the catalytic activity. A novel synthesis of W5+0.247W6+0.753O2.886/TiO2 nanomaterials via the microwave-ultrasound assisted method was reported. TiO2 nanoparticles with crystallite size around 6 nm was obtained with only 5 min microwave and ultrasound irradiation. WO3/TiO2 catalyst contained 442 μmol/g Lewis acid sites and 3.82 % oxygen defects in the WO3 crystals. For the ultralow sulfur fuel production, the WO3/TiO2 catalyst could rapidly oxidize 97 % of 4,6-dimethyldibenzothiophene (4,6-DMDBT) in 20 min using H2O2 as oxidant and formic acid as promoter in a model diesel. Formation of oxygen defects, peroxometallic species, and Lewis acid sites in catalyst surface played the key roles in the 4,6-DMDBT oxidation.