The selective oxidation of alcohols in aqueous phase over supported metal catalysts is facilitated by high-pH conditions. University of Virginia chemical engineers Robert J. Davis and Matthew Neurock have studied the mechanism of ethanol and glycerol oxidation to acids over various supported gold and platinum catalysts in alkaline water.
Labeling experiments with 18O2 and H218O demonstrate that oxygen atoms originating from hydroxide ions instead of molecular oxygen are incorporated into the alcohol during the oxidation reaction. Density functional theory calculations suggest that the reaction path involves both solution-mediated and metal-catalyzed elementary steps. Molecular oxygen is proposed to participate in the catalytic cycle not by dissociation to atomic oxygen but by regenerating hydroxide ions formed via the catalytic decomposition of a peroxide intermediate.
The selective oxidation of alcohols with molecular oxygen over gold (Au) catalysts in liquid water offers a sustainable, environmentally benign alternative to traditional processes that use expensive inorganic oxidants and harmful organic solvents. The research is seen as an important first step in unlocking the potential of using metal catalysts for developing biorenewable chemicals.
- Reactivity of the Gold/Water Interface During Selective Oxidation Catalysis
Bhushan N. Zope, David D. Hibbitts, Matthew Neurock, Robert J. Davi
Science 2010, 330 (6000), 74 – 78.