Hydrodeoxygenation of sulfoxides to sulfides by a Pt and MoOx co-loaded TiO2 catalyst

Abstract

Supported metal nanoparticle catalysts were studied for the hydrodeoxygenation of sulfoxides to sulfides under solvent-free and mild conditions (50–155 °C, 1 or 7 atm H₂). The catalytic activity for the model reaction of diphenyl sulfoxide depended on the type of metals, support materials and co-loaded oxides of transition metals (V, Nb, Mo, W, Re). Pt and MoO_x co-loaded TiO₂ (Pt–MoO_x/TiO₂) showed the highest activity. Pt–MoO_x/TiO₂ was reusable after the reaction and was effective for the reduction of various sulfoxides and showed a higher turnover number (TON) than previously reported catalysts. Using Pt–MoO_x/TiO₂, benzylphenylsulfone was reduced by H₂ to give phenylbenzyl sulfide via benzylphenyl sulfoxides, which represented the first example of catalytic conversion of a sulfone to a sulfide by H₂. Characterization studies of Pt–MoO_x/TiO₂ show that the surface of TiO₂ is covered by small (or thin layer) Mo oxide species with exposed Mo cations as Lewis acid sites, and 4–5 nm sized Pt metal nanoparticles are supported on the Mo oxide-covered TiO₂.