Production of H₂O₂ during Au/C catalyzed aerobic oxidation of 1,2-propanediol

The efficiency of H₂O₂ formation during Au/C-catalyzed aerobic oxidation of 1,2-propanediol (diol) at 35 °C increased with increasing concentrations of diol and NaOH. Diol conversion and H₂O₂ accumulation data collected at different concentrations of diol and NaOH could be fitted to a Langmuir–Hinshelwood kinetics model using the diolate as the reactant, indicating that the primary role of hydroxide ions is to deprotonate the diol and not as a reactant in the rate limiting step. Using the model to extrapolate the data to full surface coverage of diolate, it was found that one molecule of diol oxidized would produce one molecule of H₂O₂ and one molecule of lactate. At lower diolate coverages, unoccupied active sites adjacent to adsorbed hydroperoxy/peroxy enabled O[sbnd]O bond cleavage and lowered the H₂O₂ production efficiency. Catalytic degradation of H₂O₂ decreased its production efficiency, and accumulation of trace amounts of heavy products likely caused the slow catalyst deactivation.