Ether Functional Groups Enable Oxidative Dehydrogenation of Aliphatic Secondary Alcohols in Water

Aerobic oxidative dehydrogenation (ODH) of secondary alcohols is catalyzed by both platinum and platinum–bismuth catalysts in water. Symmetric 1,3-diether-2-alcohols are high-value glycerol-derived products and ODH of these alcohols to form analogous ketones over heterogeneous catalysts has not been reported previously. Reported herein are initial turnover frequencies (TOFs, per surface Pt), apparent activation energies, and apparent reaction orders for the ODH of several glycerol-derived oxygenates over Pt and PtBi particles supported on silica. Initial ODH rates were obtained from batch reactions (313–353 K, 0.01–2 M substrate). Apparent reaction orders were consistent with a rate-determining step involving alcohol α C–H bond activation over adjacent surface sites. Apparent activation energies measured in the first order kinetic regime over Pt and PtBi catalysts were similar for a range of substrates. Similar aliphatic alcohols (e.g., 2-butanol, 3-pentanol, and 4-heptanol) were not measurably converted under these conditions. Computational analysis of solvation energy, solvated binding free energy, and the binding structure collectively suggest that the experimentally observed reactivity of 1,3-dimethoxypropan-2-ol and 1,3-diethoxypropan-2-ol results from their relatively weak binding to the surface, whereas the lack of reactivity for 3-pentanol and 4-heptanol may result from them binding too strongly to the surface. These findings suggest secondary alcohol ODH occurs via a similar mechanism over Pt and PtBi particles and that the presence of ether linkages increases the rate of ODH in water.