The transient behavior of the dehydration of isopropanol has been studied in a microreactor. The av. productivity under periodic operation is found to be considerably higher compared to steady state even for conversions reaching 80%. The optimal cycle periods range from 60 to 200 s, depending on the space time. Depending of the reaction conditions an increase of the av. reactor productivity of up to 80% is obtained. The predominant influence of the catalyst capacity and the reaction rate on the length of the optimal cycle period has been emphasized. It results from this study that high frequency periodic operation is a prerequisite for fast reactions and for catalysts with a low adsorption capacity. The exptl. results could be successfully described with a mechanistic model in the whole range of exptl. conditions. The model can be applied to predict the transient behavior of different types of reactors. [on SciFinder (R)]