Roles of oxygen defects and surface acidity of Keggin-type phosphotungstic acid dispersed on SBA-15 catalysts in the oxidation of 4,6-dimethyldibenzothiophene

Abstract: Oxygen defects, surface acidity and catalytic activity of Keggin-type phosphotungstic acid dispersed on SBA-15 mesoporous catalyst were investigated. When the catalyst was calcined at different temperature, oxygen defects resulted from removal of terminal oxygen from W=O bond or cleavage of corner sharing W–Oc–W bond in the Keggin structure via dehydration or/and suface dehydroxylation. The catalyst contained both Lewis (L) and Brønsted (B) acid sites and their amount varied with the calcination temperature which could be correlated well with the conversion of 4,6-dibenzothiophene (4,6-DMDBT) in a model diesel using H₂O₂ as oxidant. L acid sites served as active sites for 4,6-DMDBT adsorption via electron donation-acception pathway and B acid sites helped oxygen transferring from peroxotungstate complex to sulfur atom in the adsorbed 4,6-DMDBT, benefiting the sulfone formation. Graphic abstract: [MediaObject not available: see fulltext.].