Spatially resolved species and temperature profiles have been measured for the catalytic partial oxidation of CH4 on autothermally operated Rh-coated alpha-Al2O3 foams in both steady state and transient mode. A probe consisting of a thin quartz capillary and a thermocouple was moved with sub-mm resolution through the catalyst/heat shield stack to sample the gases into a mass spectrometer and measure temperature. The probe was also used to follow the relaxation of the system upon perturbation by stepping the stoichiometry of the reactants periodically. The spatial profiles in steady state show that H-2 and CO are formed in presence of gas phase oxygen (oxidation zone) and after total oxygen conversion by steam reforming (reforming zone). The stepwise change of the reactant stoichiometry in the transient experiments allowed decoupling chemistry (ms timescale) and temperature (s timescale). By exposing a catalyst, initially operating very hot at C/O = 0.6, suddenly to a CH4 rich feed (C/O = 1.4), it was possible to follow how the integral H-2 and CO production rates decrease with decreasing temperature of the catalyst. The reverse switch from C/O = 1.4 to 0.6 showed how the integral H-2 and CO production rates increased with increasing temperature of the catalyst. Differential reaction rates were obtained by performing these transients spatially resolved at two adjacent points in the catalyst. For C/O = 0.6 -> 1.4, H-2 and CO formation show a strict linear Arrhenius behavior over the entire temperature range from similar to 1100 to similar to 600 degrees C. For C/O = 1.4 -> 0.6, the Arrhenius plots show two straight segments, a steep increase in the formation rate from similar to 630 to similar to 710 degrees C and a weak increase from similar to 725 to similar to 1000 degrees C. In both cases, H-2 formation is more activated than CO formation indicating two different rate determining steps. (c) 2006 Elsevier Ltd. All rights reserved.