Development of a kinetic model for the oxidation of methane over Pd/Al2O3 at dry and wet conditions

The kinetics of the oxidation of methane over a commercial 0.5% Pd on γ-Al₂O₃ catalyst has been studied in a lab-scale fixed-bed reactor, the effect of temperature, and methane, oxygen and water partial pressures being investigated, in a range of interest for environmental applications. Different Eley–Rideal, Langmuir–Hinshelwood and Mars–van Krevelen models were fitted to the experimental results, the best fitting being obtained for a Mars–van Krevelen model that considers slow desorption of the reaction products. The model parameters obtained both from differential and integral treatment of the experimental data are in good agreement with each other. A modification of the proposed model, taking into account that water is adsorbed over oxidised sites, is also able to model the inhibition produced by steam.