Synthesis of mesoporous ZnO/TiO2–SiO2 composite material and its application in photocatalytic adsorption desulfurization without the addition of an extra oxidant

Abstract

Photocatalytic adsorption desulfurization (PADS) technology has attracted enormous attention in the deep desulfurization field. Therefore, a good material with high photocatalytic activity and adsorption capacity toward organic sulfide is desirable. Herein, mesoporous ZnO/TiO₂–SiO₂ (ZTS) was synthesized for the first time and successfully applied in the photocatalytic desulfurization of dibenzothiophene (DBT). The composite materials were characterized by means of X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), N₂-physisorption, transmission electron microscopy (TEM), UV-Vis diffusive reflectance spectra (UV-Vis DRS), X-ray photo-electron spectroscopy (XPS), photoluminescence (PL) and electron spin resonance (ESR). The results show that the doping of TiO₂ promotes the photocatalytic and adsorption abilities of the catalysts dramatically. ZTS-3 with Si/Ti = 3 exhibits the best photocatalytic desulfurization activity compared with other proportions of titanium doping. The final DBT conversion can reach 97%, and the maximum adsorption of DBT over ZTS-3 is 47 mg-S per g-cat. The photocatalytic test indicates that the remarkable photocatalytic activity of ZTS is due to the formation of a heterojunction by the interaction of ZnO and TiO₂, which can successfully expand solar light absorption, improving the charge separation efficiency and inhibiting the recombination of photocatalytic electron–hole pairs. Moreover, no extra oxidants (such as O₂, H₂O₂ or an organic oxidant) were added, which is highly beneficial for the consequent treatment of the fuel and can reduce the processing cost markedly.