Improved CO-PROX Performance of CuO/CeO2 Catalysts by Using Nanometric Ceria as Support

Almerinda Di Benedetto,Gianluca Landi,Luciana Lisi

doi:10.3390/catal8050209

Almerinda Di Benedetto, Gianluca Landi + Show 1 more

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https://doi.org/10.3390/catal8050209

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Abstract

Despite of the huge number of papers about the catalytic preferential oxidation of CO (CO-PROX) for the purification of H2 streams, there is still a need for more effective catalysts in order to reduce the large required catalyst volume of CO-PROX unity. In this work, large surface area nanometric ceria was used as support for CuO/CeO2 catalysts with CuO load up to 10 wt % easily dispersed by wet impregnation. Catalysts were characterized by ICP-MS, XRD, SEM/EDS, N2 physisorption, H2 temperature programmed reduction (TPR), and CO2 temperature programmed desorption (TPD) and tested under different reaction conditions (including under feed containing inhibiting species such as CO2 and H2O). Catalytic tests revealed that our samples show high activity and selectivity even under stringent reaction conditions; moreover, they result among the most active catalysts when compared to those reported in the scientific literature. The high activity can be related to the enhanced amount of highly dispersed copper sites in strong interaction with ceria related to the nature of the nanometric support, as evidenced by the characterization techniques. Despite the high concentration of active copper sites, catalytic performance is limited by CO2 desorption from ceria in the neighborhood of copper sites, which prevents a further improvement. This suggests that new catalyst formulations should also provide a lower affinity towards CO2.

Highlights

The catalytic preferential oxidation of CO (CO-PROX) has been proposed as an effective technique to purify hydrogen streams for Proton-Exchange Membrane (PEM) fuel cells reducingCO concentration from 0.5–1 vol % to 10–100 ppm [1,2,3]
Catalysts were characterized by ICP-MS, XRD, SEM/EDS, N2 physisorption, H2 temperature programmed reduction (TPR), and CO2 temperature programmed desorption (TPD) and tested under different reaction conditions
The high activity can be related to the enhanced amount of highly dispersed copper sites in strong interaction with ceria related to the nature of the nanometric support, as evidenced by the characterization techniques

Summary

Introduction

The catalytic preferential oxidation of CO (CO-PROX) has been proposed as an effective technique to purify hydrogen streams for Proton-Exchange Membrane (PEM) fuel cells reducingCO concentration from 0.5–1 vol % to 10–100 ppm [1,2,3]. CuO/CeO2 catalysts represent a cheaper and more selective alternative to noble metals and have been widely investigated in the last decades [3,5,32,33,34], focusing on methods to further improve performance based on doping [6,8,10,18,22,35,36,37,38,39,40,41,42] or unconventional preparation methods [4,11,12,18,43,44,45,46,47]. The reason for the good performance of CuO/CeO2 catalysts was assigned to the strong interactions between copper and ceria resulting in an enhanced reducibility of both oxides [48,49,50]. Copper oxides clusters, not interacting with ceria, are recognized as active centers for the (undesired) H2 oxidation [21,52]

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