Oxidative steam reforming of methanol (OSRM) reaction was investigated over a novel monolithic ZnO-Cr2O3/CeO2-ZrO2 catalyst developed in our laboratory. A novel flat-bed reactor was designed to measure the concentration profiles of the monolithic catalyst beds under different operation conditions: water-to-methanol mole ratio (W/M)between 1 and 1.5; oxygen-to-methanol mole ratio (O/M) in the range of 0.1-0.3; space velocity ranging from 1840 to 2890 h(-1); and reaction temperature in the scale of 400-440 degrees C. On the basis of these results, reaction pathways for the OSRM were discussed. It is indicated that only three independent reactions dominate in our reaction system, namely, the partial oxidation of methanol, the steam reforming of methanol and the methanol decomposition reaction, whereas the water-gas shift and the reverse water-gas shift reactions should be ignored. In addition, the steam reforming of methanol proceeds along all the catalyst bed, whereas methanol decomposition and oxidation reactions occur mainly at the entrance of the catalyst bed. (C) 2006 Elsevier B.V. All rights reserved.