PT-CATALYZED COMBUSTION OF CH4-C3H8 MIXTURES

Experiments on a Pt foil, combined with simulations using a stagnation point flow model, were used to study the influence of propane on the combustion of methane in air over Pt catalysts. The steady-state multiplicity of the system was studied in terms of the surface temperature of the catalyst as a function of the input power. The system exhibited up to three stable steady states for some fuel ratios. Propane ignites at a much lower temperature and power input, and we observed that the whole mixture ignited at these conditions for sufficiently high propane contents. The model, which uses one-step global reaction rates for the kinetics, reproduced these results, predicting the ignition, extinction and autothermal temperatures fairly accurately. The nature of each stable state could be determined from the model. The low temperature state is the extinguished state (with negligible reaction of either fuel), the intermediate state corresponds to only propane oxidation, and the third shows oxidation of both methane and propane. The model also predicts that the system exhibits two distinct autotherms for lean methane-propane mixtures.