Structure sensitivity and kinetics of D-glucose oxidation to D-gluconic acid over carbon-supported gold catalysts

The heterogeneously catalyzed oxidation of D-glucose to D-gluconic acid over Au/C catalysts has been studied. A series of Au/C catalysts were prepared by the gold sol method with different reducing agents and different kinds of carbon support providing An mean particle diameters in the range 3-6 nm. The activities of these catalysts with respect to D-glucose oxidation were compared, and several aspects influencing activity, especially Au particle size, were discussed. The influence of reaction conditions (T = 30-90 degreesC, pH 7.0-9.5) on the kinetics of the D-glucose oxidation has been examined using the most active Au/C catalyst. By a detailed analysis of all reaction products under different reaction conditions, a reaction network of the D-glucose oxidation is presented, and a reaction mechanism for D-glucose oxidation that explains the influence of pH on reaction rate is proposed. Ensuring that D-glucose oxidation takes place in the kinetic regime (sufficient stirring rate and airflow rate), a semiempirical model based on a Langmuir-Hinshelwood-type reaction pathway is assumed. At 50degreesC and pH 9.5 kinetic parameters were calculated by an optimization routine. The resulting concentration courses of D-glucose and D-gluconic acid were in good agreement with the experimental data. All experiments were carried out in a semibatch reactor under pH control at atmospheric pressure. 2004 Elsevier Inc. All rights reserved.