Surface acid–basic properties of WOx–ZrO2 and catalytic efficiency in oxidative desulfurization

Abstract

The dependence between catalytic activity of WOx–ZrO2 system in the oxidation of dibenzothiophene (DBT) and its relationship with local acidity has been explored experimentally and theoretically. The structural requirements indicate that the oxidative efficiency (per W-atom) increases as the WOx surface density becomes larger, up to 7W/nm2. These results strongly suggest that n-meric domains and/or WO3−x nanoparticles (NPs) anchored to surface are more reactive than monomeric and three-dimensional structures and that WOx domains of intermediate size provide the better compromise between surface acidity and catalytic efficiency. The experimental results suggest that catalytic efficiency is favored by the increasing of Brönsted acidity density. The theoretical analysis reveals that the combined presence of Lewis and Brönsted sites energetically favored the formation of peroxometallate complexes and that OOH addition reaches its maximum for minimum (non-zero) number of Lewis sites and maximum number of Brönsted sites.