Photooxidative–extractive deep desulfurization of diesel using Cu–Fe/TiO2 and eutectic ionic liquid

• Catalyst average recyclability was 99.75%.
• 100% sulfur conversion using 2.0_Cu–Fe/TiO2 for model oil and diesel fuel using.
• Sulfur removal for model oil was 97.06% and 2.94% in the 1st and 2nd extraction.
• Sulfur removal for diesel fuel was 78.93% and 21.07% in the 1st and 2nd extraction.
• Extractant used was choline chloride eutectic based ionic liquid.

An efficient photooxidative–extractive system for deep desulfurization of model fuel and actual diesel fuel was explored. A series of bimetallic Cu–Fe/TiO2 photocatalysts was synthesized using sol–gel hydrothermal method and characterized using thermogravimetric analysis (TGA), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) coupled with energy dispersive X-ray analysis (EDX), high resolution transmission electron microscopy (HRTEM) and diffuse reflectance UV–visible spectroscopy (DR-UV–Vis). The photocatalysts were evaluated for photooxidative–extractive deep desulfurization of model oil (100, 300 and 500 ppm dibenzothiophene in dodecane) and actual diesel fuel. 2.0 wt% Cu–Fe/TiO2 photocatalyst was identified as the most efficient photocatalyst for the conversion of sulfur species under mild conditions in the presence of hydrogen peroxide (H2O2:S molar ratio of 4) as oxidant and eutectic based ionic liquid as extractant. The sulfur conversion in both model oil and actual diesel fuel reached 100%. The removal of sulfur species from both model oil and actual diesel fuel was done by two times extraction with a removal of 97.06% and 78.93%, respectively in the first run and 2.94% and 21.07%, respectively in the second run. The photocatalyst was able to be recycled for six cycles with an average performance of 99.75%.