In this work dynamic and steady-state CH4 partial oxidation tests, performed in an insulated lab-scale reactor over a Rh-based catalyst supported onto Al2O3 spheres, are presented and discussed. To gain insight in the complex observed phenomena a previously developed ID heterogeneous mathematical model of adiabatic reactor was applied to data analysis. The model implemented an indirect reaction scheme independently derived in previous works. In experiments at low flow rates the heat dispersion significantly affected the steady-state response of the reactor; the process was governed by thermodynamics. By increasing the flow rate the catalytic bed progressively heated up and the adiabatic behavior was approached as a result of the predominance of the reaction enthalpy release over the heat losses; a kinetic effect of contact time was observed. Under these conditions start-up dynamics of the process were acquired. The temporal evolution of the product distribution along with the shape of axial temperature profiles at steady state were consistent with the occurrence of an indirect reaction path leading to the formation of synthesis gas. A sensitivity analysis showed that the description of the temperature profiles and conversion/selectivity performances at steady state is greatly influenced by the rate of the reforming reactions; the simulation of the reactor start-up dynamics is highly sensitive to the initial solid temperature. The comparison between measured temperature profiles and model predictions suggested that the thermocouple measurements were mainly influenced by the temperature of the flowing gas. (c) 2006 American Institute of Chemical Engineers.