The Green Preparation of Mesoporous WO[sub.3]/SiO[sub.2] and Its Application in Oxidative Desulfurization

Recently, supported WO[sub.3] -based catalysts have been widely used in oxidative desulfurization (ODS) due to their advantages of easy separation, high activity, and being environment-friendly. In this work, supported mesoporous WO[sub.3] /SiO[sub.2] catalysts have been prepared using an incipient-wetness impregnation method with agricultural waste rice husks as both a silicon source and mesoporous template, and phosphotungstic acid as a tungsten source. The effects of different calcination temperatures and WO[sub.3] loadings on the ODS performance of samples are studied, and the appropriate calcination temperature and WO[sub.3] loading are 923 K and 15.0 wt.%, respectively. The relevant characterization results show that, compared with pure WO[sub.3] , the specific surface area and mesopore volume of WO[sub.3] /SiO[sub.2] samples are greatly increased. Due to (a) high WO[sub.3] loading, (b) high specific surface area, and (c) nanoscale WO[sub.3] grains uniformly dispersed on the surface of the mesoporous SiO[sub.2] carrier, active sites of WO[sub.3] /SiO[sub.2] catalysts are greatly increased, and their catalytic activities are improved. After the sixth and eighth runs in the ODS of dibenzothiophene and 4,6-dimethyldibenzothiophene, respectively, the WO[sub.3] /SiO[sub.2] catalyst still maintains high catalytic activity (>99.0%) despite the presence of a partial loss of WO[sub.3] . In addition, with the aid of the UV-Vis technique, the tungsten-peroxo species, the active intermediates in the ODS reaction catalyzed by the WO[sub.3] /SiO[sub.2] catalyst, are captured. Finally, a possible mechanism for the ODS of bulky organic sulfides using the WO[sub.3] /SiO[sub.2] catalyst is proposed.