Perspectives on the kinetics of diol oxidation over supported platinum catalysts in aqueous solution

• Carbon chain size influenced the rate and selectivity of α,ω-diol oxidation.
• The proximity of a second alcohol decreased the rate of terminal alcohol oxidation.
• Reaction orders for O2 and alcohol were evaluated at different start-up conditions.
• Kinetic isotope effect verified kinetic relevance of C–H activation.
• A two-site kinetic model for Pt-catalyzed alcohol oxidation was proposed.

The catalytic oxidation of a variety of terminal alcohols was performed over Pt/C with 10 bar dioxygen at 343 K in aqueous solvent at low pH. The influences of Pt particle size, carbon support, alcohol structure, and start-up conditions were explored. Although the turnover frequency was not affected by particle size or the carbon support, the structure of the alcohols affected their initial rate of conversion. Both the rate of oxidation of α,ω-diols and selectivity of the diols to the diacids increased with increasing carbon chain length. The rate of 1,6-hexanediol oxidation was independent of dioxygen pressure and the order of reaction with respect to diol concentration depended on the start-up conditions. A kinetic model involving two types of metal sites was proposed to account for the experimental observations.

The oxidation of mono-alcohols and α,ω-diols to aldehydes over supported Pt was evaluated at acidic aqueous conditions to elucidate the effects of carbon chain length and functionality on the rate of reaction. The proximity of a second alcohol group decreased the TOF of alcohol oxidation.Figure optionsDownload high-quality image (84 K)Download as PowerPoint slide