Microstructured catalysts used for methane steam reforming in microchannel reactors are mathematically described and experimentally demonstrated under realistic process conditions. A heterogeneous model has been developed with a graphical interface to represent the three dimensions of the microchannel reactor. Porous metal substrates (FeCrAlY) were used to form engineered catalysts with active precious metal (Rh) for methane steam reforming. Two types of structures were evaluated in the microchannel reactors and simulated with the developed heterogeneous reactor model. Local temperature and methane concentration profiles within the structures are illustrated to show the correlation of the catalyst structure and its performance. Such a modeling technique provides a convenient and flexible method to evaluate variables in designing more efficient catalysts for the highly endothermic steam reforming reactions, as the desired mass and heat transfer characteristics are achieved. (c) 2005 Elsevier B.V. All rights reserved.