Keggin heteropolycompounds as catalysts for liquid-phase oxidation of sulfides to sulfoxides/sulfones by hydrogen peroxide

H4PMo11VO40, H5PMo10V2O40 and H9PMo6V6O40 acids and an acidic pyridinium salt of H4PMo11VO40 were synthesized. They were characterized by FT-IR and the variations of their acid properties were determined by titration with n-butylamine. They proved to be highly active and selective catalysts for the hydrogen peroxide oxidation of methyl phenyl sulfide to the corresponding sulfoxide or sulfone. The conversion and selectivity results may be explained in terms of the co-existence of acidic and oxidative properties in the catalysts. On the other hand, a convenient catalytic homogeneous procedure has been found to oxidize different sulfides to sulfoxides or sulfones, with 35% aqueous H2O2, using (PyH)H3PMo11VO40 as catalyst. The oxidation reaction is carried out at room temperature for sulfoxides or 40 °C for sulfones and requires a short time. The sulfoxides or sulfones were obtained with excellent yields by controlling the amount of H2O2.

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► Keggin heteropolycompounds as catalysts for ecofriendly liquid phase oxidation.
► Pyridinium salt of H4PMo11VO40, H4PMo11VO40, H5PMo10V2O40 and H9PMo6V6O40 acids.
► Aqueous hydrogen peroxide as a clean oxidant.
► Selective oxidation of sulfides to sulfoxides or sulfones.