Ignition and extinction in the catalytic oxidation of hydrocarbons over platinum

The ignition- extinction behavior in the oxidation of methane, ethane, propane and isobutane, as well as of ethylene and propylene over a platinum-foil catalyst was studied over the entire range of fuel/air ratios at atmospheric pressure. Ignition and extinction of the heterogeneous surface reaction, homogeneous ignition and the autothermal behavior of these fuel-air mixtures were investigated. The results show a common trend in the ignition extinction behavior of the alkanes and a different trend for the olefins. This is discussed in terms of a simple model, which correctly predicts the composition dependence of the surface ignition curve for reasonable values of parameters, indicating a mainly oxygen-covered surface during ignition of the alkanes and a mainly hydrocarbon-covered surface in the case of the olefins. Different branches of the complete bifurcation diagrams are discussed separately, allowing qualitative conclusions about the catalytic activity of Pt for the oxidation reactions of different fuels.