Development of water gas shift supported catalysts for fuel processor units

Fuel Cell (FC) technology promises to be a viable alternative for small scale electric heat and power generation (combined heat and power units, CHP). Moreover, the polymer electrolyte membrane FC (PEM-FC) is currently considered the most suitable technology for vehicles, both for traction and as auxiliary power unit APU; the latter is used on boats and yachts too. The ideal fuel for the PEM-FC is pure H2 gas. However, due to the lack of H2 distribution infrastructures, the current way of producing H2 to feed PEM-FC involves the reforming of hydrocarbon feedstocks and the removing of the catalyst poison CO with a series of catalytic steps. Water Gas Shift (WGS) is an attractive option for CO conversion although, due to its exothermic nature (ΔH298°C = -41.1 kJ·mol-1), the equilibrium conversion is thermodynamically limited at high temperatures. In contrast, at low temperatures, the reaction rate is constrained by kinetics such that highly performing catalysts are necessary to provide adequate activity. For these reasons two WGS stages are generally employed: a high temperature stage (HT-WGS), which takes place between 400-500°C and reduces the CO concentration to about 2-5%, followed by a second shift at a lower temperature (LT-WGS), with a cooling stage in between, which is carried out over a temperature range of 200-400°C and reduces the CO concentration to about 0.5-1%. In this work, catalysts based on Pt and mixed Pt+Re on different supports were prepared and their catalytic activity was tested; moreover, a comparison with commercial catalysts was also carried out. Very promising results were obtained in the HT-WGS range as the catalytic performances of the prepared catalysts were superior to those reached by the commercial catalyst; therefore they can be considered as possible candidates for FC technology. Copyright © 2007 The Berkeley Electronic Press. All rights reserved.