In catalytic partial oxidation of methane under isothermal conditions, a 0.3 wt% Rh/MgO catalyst modified with Co at a molar ratio of Co/Rh = 1 gave greater CH4 conversion and selectivity to CO and H-2 than unmodified 0.3 wt% Rh/MgO. Characterization results using ternperature-progranuned reduction, extended X-ray absorption fine structure, and transmission electron microscopy demonstrated alloy formation between Rh and Co. In catalytic partial oxidation of methane without N-2 dilution, the Rh-Co/MgO catalyst with Co/Rh = 1 suppressed the temperature increase near the catalyst bed inlet and yielded a Hat temperature profile. This behavior can be interpreted as greater selectivity in the direct partial oxidation route in the presence of gas-phase oxygen and lower activity in the steam reforming of methane in the absence of gas-phase oxygen. The better performance of Rh-Co/MgO (Co/Rh = 1) compared with Rh/MgO may result from greater methane dissociation and reduction degree during the partial oxidation of methane. (c) 2008 Elsevier Inc. All rights reserved.