Kinetics of methanol-steam reformation in an internal reforming fuel cell

Abstract

A study of the kinetics of the methanol-steam reformation reaction within an idealized tube reactor and within a non-ideal internal reforming fuel cell (IRFC) was performed. Kinetic expressions were calculated from the reaction rate data obtained from the tube reactor by least squares fitting to general power law model, as well as to a mechanism-based model put forth by Peppley et al. [Appl. Catal. A 179 (1999) 21; Appl. Catal. A 179 (1999) 31] assuming isothermal plug flow behavior. Reaction rate data obtained from an IRFC with and without an H 3PO 4 containing membrane electrode assembly (MEA) was compared to the reaction rates predicted by the kinetic model. It was found that methanol conversion rates in the IRFC were significantly less than would be for an ideal plug flow reactor (PFR) with an equal amount of catalyst due to the non-ideal flow through the reactor bed. However, despite the non-ideal flow caused by the design compromises inherent in an IRFC and the resulting drop in effective catalyst activity, it was projected that for fuel cell systems with a current density greater than 400 mA cm −2, the IRFC would require less catalyst mass than a traditional system with external reformer. This is the result of an experimentally verified accelerated methanol conversion rate in the IRFC caused by the extraction of H 2 from the reforming reactor bed. Long-term stability of the IRFC due to acid leaching still needs to be addressed. Additionally, the extraction of H 2 from the reformer bed, which occurs in the IRFC, introduces concerns of failure due to coking.