This work presents a model of a fixed-bed reactor for the catalytic partial oxidation of methane to synthesis gas at short contact time. The transient model, one dimensional in space, accounts for separate energy equations for the gas and solid phases, interphase heat and mass transfer, internal radiation within the fixed bed, longitudinal gas-phase dispersion, and detailed surface kinetics. The model is used to analyze the influence of the feedstock composition and temperature on the conversion and selectivity reactor performance. Furthermore, the study also investigates the blowout of the reaction and the impact of reactor geometry on the performance. Reactor scale-up is discussed and a general criterion is formulated. (C) 2004 American Institute of Chemical Engineers.