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 pl atinum-foil catalyst was studied over the entire range of fuel/air rat ios at atmospheric pressure. Ignition and extinction of the heterogene ous surface reaction, homogeneous ignition and the autothermal behavio r of these fuel-air mixtures were investigated. The results show a com mon trend in the ignition extinction behavior of the alkanes and a dif ferent trend for the olefins. This is discussed in terms of a simple m odel, which correctly predicts the composition dependence of the surfa ce ignition curve for reasonable values of parameters, indicating a ma inly oxygen-covered surface during ignition of the alkanes and a mainl y hydrocarbon-covered surface in the case of the olefins. Different br anches of the complete bifurcation diagrams are discussed separately, allowing qualitative conclusions about the catalytic activity of Pt fo r the oxidation reactions of different fuels.