Optimization of methane reforming in a microreactor—effects of catalyst loading and geometry

In this paper, the effect of the catalyst surface site density (catalyst amount) and reactor geometry on the reforming process of methane in a wall-coated, single-channel microreactor is investigated numerically. Such a reactor, consisting of a tubular flow channel and a thermal conductive channel wall, is a good representation of microfabricated channels and monoliths. It is found that the hydrogen selectivity changes significantly with varying catalyst loading, which is a noteworthy result. Thus, the reaction path leading to higher hydrogen production becomes more important by increasing the catalyst surface site density on the active surface. This is due to the splitting rate of methane and water, which is a function of catalyst density. Furthermore, this study shows the significance of scaling the inlet volume flow not only with the reactor volume (gas space velocity) but also with the catalyst amount (catalyst space velocity). Another unexpected result is the presence of an optimum channel geometry and an optimum catalyst amount if the gas space velocity and the catalyst space velocity are constant. This underlines the necessity of coordinating the channel diameter, the inlet volume flow rate, and the catalyst amount in order to obtain a maximum reformer performance. Furthermore, it is necessary to specify the catalyst amount, the inlet conditions and the geometry in order to characterize sufficiently a catalytic reactor.