Ultra-deep adsorptive desulfurization of light-irradiated diesel fuel over supported TiO₂-CeO₂ adsorbents

This study investigates ultra-deep adsorptive desulfurization (ADS) from light-irradiated diesel fuel over supported TiO₂-CeO₂ adsorbents. A 30-fold higher desulfurization capacity of 95 mL of fuel per gram of adsorbent (mL-F/g-sorb) or 1.143 mg of sulfur per gram of adsorbent (mg-S/g-sorb) was achieved from light-irradiated fuel over the original low-sulfur fuel containing about 15 ppm by weight (ppmw) of sulfur. The sulfur species on spent TiO₂-CeO₂/MCM-48 adsorbent was identified by sulfur K-edge XANES as sulfones and the adsorption selectivity to different compounds tested in a model fuel decreases in the order of indole > dibenzothiophenesulfone adibenzothiophene > 4-methyldibenzothiophene > benzothiophene > 4,6-dimethyldibenzothiophene > phenanthrene > 2-methylnaphthalene ∼ fluorene > naphthalene. The results suggest that during ADS of light-irradiated fuel, the original sulfur species were chemically transformed to sulfones, resulting in the significant increase in desulfurization capacity. For different supports for TiO₂-CeO ₂ oxides, the ADS capacity increases with a decrease in the point of zero charge (PZC) value; for silica-supported TiO₂-CeO₂ oxides (the lowest PZC value of 2-4) with different surface areas, the ADS capacity increases monotonically with increasing surface area. The supported TiO₂-CeO₂/MCM-48 adsorbent can be regenerated using oxidative air treatment. The present study provides an attractive new path to achieve ultraclean fuel more effectively.