Abstract
The water gas shift activities of Cu on ceria and Gd doped ceria have been studied for the further enhancement of hydrogen purity [1] after the steam reforming of ethanol. The catalytic properties of commercial catalysts were also studied to compare with the as-prepared catalysts. Copper-containing cerium oxide materials are shown in this work to be suitable for the high temperature. Copper-ceria is a stable high-temperature shift catalyst, unlike iron-chrome catalysts that deactivate severely in CO 2 -rich gases. We found that 5%Cu/10%GDC(D) has much higher activity than other copper ceria based catalysts. The finely dispersed CuO species is favorable to the higher activity, which explained the activity enhancement of this catalyst. The kinetics of the WGS reaction over Cu catalysts supported by mixed oxide materials were measured in the temperature range 200-400 °C. An independence of the CO conversion rate on CO 2 and H 2 was found.
Highlights
The water-gas shift (WGS) reaction (CO + H2O CO2 + H2) plays an important role in fuel processing
For PEM fuel cell applications, novel low-temperature WGS catalysts are under development to upgrade the hydrogenrich reformate gas streams where the catalyst possesses improved activity and greatly improved stability over the commercial Cu–ZnO catalysts [1,2]
Ceria-based catalysts are very good WGS catalysts [6,7,8,9], and the Cu–CeO2 system was first reported by Li et al as a promising lowtemperature shift catalyst [6]
Summary
The water-gas shift (WGS) reaction (CO + H2O CO2 + H2) plays an important role in fuel processing. For PEM fuel cell applications, novel low-temperature WGS catalysts are under development to upgrade the hydrogenrich reformate gas streams where the catalyst possesses improved activity and greatly improved stability over the commercial Cu–ZnO catalysts [1,2]. For a practical fuel cell system, operating under frequent shutdown and restart cycles, ceria needs to be modified by addition of zirconia [10] or another dopant to avoid formation of Ce(III) hydroxycarbonate during shutdown to RT in the watercontaining reaction gas Another approach is to regenerate the catalyst frequently by oxidation at 400– 450 oC [10,11] or to run the reaction in oxygen-assisted mode [11]. Ceria and doped ceria remains the support of choice when a highly dispersed metal preparation is desired, which must remain stable over a wide temperature range [9]; and when surface oxygen availability to the metal is required, as in the case of the water-gas shift reaction [8]
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