SCILLs as selective catalysts for the oxidation of aromatic alcohols

The cryptomelane form of manganese oxide, OMS-2, has been used a pure material as well as a 5 wt % Pt/OMS-2 catalyst for the oxidation of benzyl alcohol. In addition, these catalysts have been modified with ionic liquids via a thin layer of [Bmim][NTf₂] or [Bmpyr][NTf₂]. These catalysts were characterized using a series of techniques: NMR, XRD, DRIFT, Raman, BET, Dynamic Light Scattering, XPS, TEM, SEM. The Weisz–Prater criterion has also been considered to inform whether the reactions were under diffusional control. The presence of platinum on the OMS-2 surface results in the support transforming to form Mn₃O₄ during reaction. In contrast, in the presence of the ionic liquid, the catalysts exhibited an increased phase stability. Efficient oxidation of benzyl alcohol was observed with a conversion of 80% and 82% selectivity to aldehyde for 5 wt% Pt/OMS-2/[Bmim][NTf₂] in air. As expected an increase of the oxygen pressure led to an increase in the conversion to the detriment of aldehyde selectivity. The catalytic tests also showed an important effect on the conversion and selectivity of benzyl alcohol as a function of the diluent gas comparing inert (N₂, He, Ar) or (CO₂) reactive gases. This effect was influenced by the nature of the ionic liquid present.