Platinum catalysed aqueous alcohol oxidation: model-based investigation of reaction conditions and catalyst design

A dynamic transport model is derived to describe the platinum catalysed aqueous alcohol oxidation, considering a single spherical catalyst particle surrounded by a stagnant liquid film. The transport model is based on a heterogeneous kinetic model with mass transfer and intra particle diffusion resistances. The developed model uses the kinetic model of Markusse et al. (Catal. Today 66 (2001) 191) and is validated with the experimental kinetic data of methyl alpha-D-glucopyranoside (MGP) oxidation obtained by Vleeming et al. (Ind. Eng. Chem. Res.). The model is used to investigate the effect of process conditions, catalyst and particle properties, and transport parameters on the performance of the catalyst for alcohol oxidation. It is found that the electron conductivity of the catalyst support affects the rate of MGP oxidation especially at low bulk liquid oxygen concentrations, while at high bulk liquid oxygen concentrations, the catalyst support conductivity does not play a role. A major cause of catalyst deactivation is over-oxidation under oxygen rich conditions. This can be reversed by applying redox-cycle operation, an alternating exposure of the catalyst to oxidative and reductive environments. The advantages of redox-cycle application are demonstrated using the developed model. For reactions of negative order, such as MGP oxidation, at high bulk oxygen concentrations (C-O2,C-L > 0.3 mol/m(3)), concentrating the active catalytic material in a layer buried some distance from the surface (core) gives considerable better performance than the conventional "egg shell" design of shallow deposition near the surface or uniform distribution. However, at low bulk oxygen concentrations (C-O2,C-L less than or equal to 0.3 mol/m(3)), the performance of the uniform or egg shell distribution catalyst is superior to the core catalyst. (C) 2002 Elsevier Science Ltd. All rights reserved.