The decomposition of hydrogen peroxide, promoted by a manganese oxide catalyst supported on gamma-alumina, has been studied in three different reactors. A batch reactor was used for catalyst screening and for studying the reaction kinetics, whereas a tubular continuous reactor was used for catalyst life testing and manganese loading optimization. In fact, a progressive deactivation was observed passing from 80% to 30% conversion. The final value of conversion remained unchanged for a long time The deactivation was due to partial manganese dissolution. On the contrary, a residual activity was observed, because the undissolved manganese oxide was more strongly bonded to the alumina surface. Therefore, by reducing the amount of loaded manganese from 5 to 2 wt %, a stable catalyst was obtained. Then, catalysts containing different amounts of manganese oxide (up to 2 wt %) were prepared and tested in a kinetic study. The same catalysts were deposited as catalytic coatings on the channels wall of microchanneled stainless steel plates and tested for coating stability. Finally, the best catalyst was also deposited on the walls of a microreactor to verify the possibility of process intensification. The kinetic law derived from the batch runs was successfully used to simulate the performance of the microreactor.