H2O2-assisted hydrothermal synthesis of TiO2-SiO2 and its enhanced photocatalytic-adsorptive desulfurization performance for model fuel

Photocatalytic-adsorptive desulfurization of model fuel by the H 2 O 2 -assisted synthesized TiO 2 -SiO 2 (TiO 2 -SiO 2 -H) was investigated using air as the oxidant under UV irradiation. TiO 2 -SiO 2 -H was synthesized hydrothermally in the presence of H 2 O 2 and characterized by scanning electron microscopy (SEM), N 2 adsorption, X-ray diffraction (XRD), UV–vis diffuse reflectance spectroscopy (UV–vis DRS) and photoluminescence spectrum (PL). Compared to TiO 2 -SiO 2 synthesized in the absence of H 2 O 2 , Ti 0.25 SiO y -H showed greatly enhanced photocatalytic-adsorptive desulfurization performance due to its increased surface area, greatly increased UV absorption and decreased recombination of photogenerated hole/electron pairs. The Ti/Si molar ratio was optimized to 0.3 with the sulfur removal of 100% after reaction for 1 h at the fuel-to-Ti 0.3 SiO y -H weight ratio of 20, and the sulfur content could still be reduced to be <1 ppmw when the fuel-to-Ti 0.3 SiO y -H weight ratio was increased to 80. Moreover, TiO 2 -SiO 2 -H based photocatalytic-adsorptive process bears high selectivity for removing organosulfur in the toluene-containing fuel. The sulfur removal for model fuel containing 25 wt% toluene could reach 98.4% after reaction for 5 h. The photocatalytic-adsorptive selectivity of Ti 0.3 SiO y -H for organosulfur compounds in model diesel fuels followed the order of dibenzothiophene > 4,6-dimethyldibenzothiophene > benzothiophene. The desulfurization performance of TiO 2 -SiO 2 -H was basically stable after four consecutive desulfurization-regeneration cycles.