Direct synthesis of ordered meso/macrostructured phosphotungstic acid/SiO2 by EISA method and its catalytic performance of fuel oil

A series of ordered meso/macrostructured phosphotungstic acid (HPW)/SiO2 materials were synthesized by evaporation-induced self-assembly (EISA) method using nonionic surfactant (P123) and monodispersed polystyrene (PS) spheres as templates. SEM images displayed close-packed ordered macropores with an average pore size of 210 nm. TEM, small-angle XRD and N-2 adsorption-desorption isotherms confirmed the existence of two-dimensional (2D) hexagonal (p6mm) mesostructure, embedded in the wall of macropores. The wild-angle XRD and FT-IR spectra proved that the Keggin-type HPW were finely dispersed in a silica matrix. The composite materials were used as catalysts for oxidative desulfurization of model oil (ODS). Compared with the ordered meso/macroporous HPW/SiO2 catalyst and ordered macroporous HPW/SiO2 catalyst prepared by colloidal crystal template method, ordered meso/macroporous HPW/SiO2 catalysts synthesized through EISA method displayed much higher catalytic activity of thiophenol, dibenzothiophene (DBT) and its alkyl derivatives, achieving the thiophenol, BT, DBT, 4-MDBT and 4,6-DMDBT conversions of 100%, 83.3%, 99.3%, 89.1% and 86.5% within 40 min under the optimum conditions. This feature may be attributed to the larger mesoporous specific surface area and peculiar hierarchically meso/macroporous structural characteristics of the catalyst. Moreover, the catalytic activity has no obviously decreased even after sixth cycle of uses.