A one-dimensional two-phase reactor model for the oxidation of methane to synthesis gas over platinum in a monolith reactor is presented. The model incorporates a detailed elementary step reaction mechanism for methane oxidation, which is verified against experimental data. A good quantitative agreement with steady-state experiments and qualitative agreement with ignition experiments is achieved. The importance of individual reaction steps, homogeneous side reactions, acid main reactor parameters are investigated. Essential steps in the catalytic reaction mechanism as well as crucial reactor parameters are identified. It is shown that the reaction system is strongly dominated by competition for oxygen on the catalyst surface. Conclusions about optimal reactor configurations are discussed.