Selective Oxidation of Glucose using Hydrogen Peroxide as an Oxidant: On the Structure Sensitivity of the Apparent Activation Energy

The selective oxidation of glucose to gluconic acid with hydrogen peroxide was studied using different heterogeneous catalysts with alumina (Al2O3) and titanium silicate (TS-1, TiMWW) as supports and different noble (Au, Pd) and non-noble metals (Fe, W) as the catalytically active phases. Supported tungsten oxide catalysts showed a moderate selectivity and activity compared to palladium and iron catalysts. The best performance in the selective oxidation of glucose among the studied catalysts was displayed by gold on alumina. For this kind of catalyst, the structure sensitivity in glucose oxidation was explored, revealing a maximum rate shifted to larger gold particle sizes at higher temperatures in comparison with other studies involving activation of molecular oxygen on gold particles. A significant change in the apparent activation energy was established while changing the particle size of gold. These changes of the activation energy were adequately explained by a theoretical model for the cluster size dependence of the apparent activation energy.