Liquid Phase Oxidation of Benzyl Alcohol over Pt and Pt–Ni Alloy Supported on TiO2: Using O2 or H2O2 as Oxidant?

Abstract

Benzyl alcohol can be oxidized selectively to benzaldehyde over platinum-based catalysts using either oxygen (O₂, supplied in the form of synthetic air) or the more powerful hydrogen peroxide (H₂O₂) as the oxidant. Here we compare these oxidants in the aqueous phase oxidation of benzyl alcohol in a batch reactor at 363.15 K or 393.15 K over monodisperse Pt and Pt–Ni nanostructures synthesized with molybdenum hexacarbonyl (Mo(CO)₆) as a reductant. The initial catalytic activity of either Pt or a Pt–Ni alloy anchored on titania support (TiO₂) is much higher when using H₂O₂ than when using O₂ (supplied in the form of synthetic air). However, the high initial activity using H₂O₂ is accompanied by a strong decrease in the activity over Pt. Alloying Pt with Ni results in a reduction in the activity in the benzyl alcohol oxidation when using O₂ but enhances the initial activity when using H₂O₂. The results are rationalized based on a change in the relative surface concentration of oxygen-containing species upon changing the oxidant or alloying Pt with Ni.

Graphic Abstract