Catalytic adsorptive desulfurization of model diesel fuel using TiO2/SBA-15 under mild conditions

• Proposed a new CADS–TiO2/SBA-15 system for ultra-deep desulfurization of fuel.
• High CADS capacity of 12.7 mg/g at low S-conc. of 15 ppm-S was achieved.
• Fast CADS kinetic equilibrium was achieved in 0.5 h.
• Excellent regenerability of TiO2/SBA-15 by oxidative air treatment was reported.

This study investigates catalytic adsorptive desulfurization (CADS) of model diesel fuel using TiO2/SBA-15 under mild conditions. The TiO2/SBA-15 was prepared by a facile incipient wetness impregnation method and characterized by N2 adsorption and X-ray diffraction. The CADS referred to ADS performance were evaluated in a batch reactor. High desulfurization uptake of 12.7 mg/g was achieved at low sulfur concentration of 15 ppmw-S by TiO2/SBA-15 under CADS, which was two-magnitude higher than that under ADS without the in-situ catalytic oxidation of dibenzothiophene. Kinetic results suggested that the CADS equilibrium over TiO2/SBA-15 was reached fast in 0.5 h. In the CADS–TiO2/SBA-15 system, the TiO2 loading, cumene hydroperoxide/dibenzothiophene ratio and CADS temperature were optimized to be 10 wt%, 2, and 35 °C, respectively. Furthermore, desulfurization tests in 5 consecutive CADS-regeneration cycles suggested that the bi-functional TiO2/SBA-15 can be regenerated by acetonitrile washing followed with oxidative air treatment. The CADS–TiO2/SBA-15 mechanism went through the oxidation of DBT to oxidized DBTO2 over TiO2/SBA-15 by cumene hydroperoxide, which was followed by the adsorption of the oxidized DBTO2 over TiO2/SBA-15. The superior desulfurization uptake at low sulfur concentration range, fast adsorption kinetics, excellent regenerability, operation at mild conditions, and facile and low-cost adsorbent synthesis make the CADS–TiO2/SBA-15 system an effective and economic desulfurization approach for ultra-clean fuel production.