A new device with microwave irradiation has been developed to trigger hydrogen generation from a water gas shift reaction (WGSR) in this study. In the experiments, the effect of a high-temperature catalyst on the WGSR is investigated. The results indicate that the increase of hydrogen generation tends to slow down once the gas hourly space velocity (GHSV) decreases and approaches 28,000 h(-1). When the steam/CO ratio is low, for example, steam/CO = 1, a concave up curve of CO concentration, characterized by conventional heating methods is not observed a microwave irradiation environment This comparison,. shows that the performance of the WGSR with microwave irradiation is better. It is noted, however, that cracks may occur on the catalyst surface as a result of less water to relieve the high thermal gradient, stemming from the microwave radiation on the catalyst bed. With an increase in the reaction temperature or steam/CO ratio, a smoother increase in CO conversion is observed, as opposed to those observed in conventional heating methods. This is attributed to the fact that the energy absorption by steam and the catalyst is more efficient under the effects of microwave radiation. As a whole, this study shows that the microwave reactor heats faster, provides more efficient energy transfer to reactants and minimizes the space needed to achieve the desired results. (c) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.