Kinetics for the partial oxidation of methane on a Pt gauze at low conversions

Intrinsic kinetics of the catalytic partial oxidation of methane were studied at atmospheric pressure in the presence of transport limitations using a single Pt gauze. Catalyst temperature and gas-phase temperatures were measured directly. CO, CO2, and H2O were the main products at catalyst temperatures between 1,030 and 1,200 K, residence times of 0.02 to 0.2 ms, CH4/O-2 ratios between 1.8 and 5.0, and O-2 conversions between 9 and 46%. A kinetic model was developed that consists of six reaction steps. Methane adsorption had to be considered as oxygen-assisted to describe the experimental data, in particular the decrease of the selectivity for CO with increasing space times. Corresponding intrinsic kinetic parameters were obtained from the literature and from regression of the experimental CO selectivities. The calculated conversions and selectivities were obtained using the intrinsic kinetic model, together with a reactor model accounting for no transport limitations quantitatively without any adjustable parameter. Simulations indicate initial CO selectivities between 86 and 96% over the investigated range of conditions, and illustrate the relevance of both surface kinetics and mass transport in CO formation.