Effect of the presence of CuOx on the catalytic behavior of bimetallic Au-Cu catalyst supported on Ce-Zr mixed oxide in CO preferential oxidation

Juan David Arevalo,Luis Fernando Córdoba,Julio César Vargas

doi:10.15446/ing.investig.v39n2.76586

Juan David Arevalo, Luis Fernando Córdoba + Show 1 more

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https://doi.org/10.15446/ing.investig.v39n2.76586

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Abstract

The effect of the presence of copper was evaluated on a bimetallic catalyst Au-Cu based on mixed oxide cerium-zirconium in the preferential oxidation of CO (CO-PROX). Six catalytic materials, based on mixed oxides, were prepared: (1) the support (CeZr); (2) the monometallic catalysts, i.e. gold (Au/CeZr), (3) impregnated copper oxide (CuOx/CeZr) and (4) incorporated copper (CuCeZr); and the bimetallic catalysts, i.e. (5) impregnated copper oxide and gold (Au-CuOx/CeZr), and (6) gold and incorporated copper (Au/CuCeZr). The catalysts were evaluated in the CO-PROX in the range 30-300°C and atmospheric pressure, where the Au-CuOx/CeZr showed the best catalytic behavior. The influence of CO2 and H2O in the feed stream was evaluated on the catalytic performance of the Au-CuOx/CeZr. An inhibitory effect for the CO2 was observed, while the presence of H2O enhanced the performance. Additionally, the catalytic stability was evaluated, reaching CO conversion of 93% and selectivity of 90% for 118 h. The catalytic materials were characterized by XRD, showing in all cases the fluorite cubic structure. The N2 adsorption-desorption analyses showed that synthesized materials were mesoporous and the TPR-H2 test reveals that the presence of the active phase increases the reducibility of Ce4+ to Ce3+. Reduction peaks of the gold catalyst were present at lower temperatures than those of the copper catalyst, which is related to a hydrogen spillover phenomenon. Finally, the samples were analyzed by SEM and TEM, which confirmed the formation of nano-particles with a diameter of about 4 nm.

Highlights

Proton Exchange Membrane Fuel Cells (PEMFC) are very interesting in portable applications, since they generate energy from hydrogen with high efficiency, reduced emissions and quick responses to charge changes (Salemme, Menna, Simeone and Volpicelli, 2010)
The present study proposes to evaluate the cooperative effect between gold and copper oxide supported on cerium-zirconium mixed oxides in the CO-PROX reaction
Six catalytic materials were prepared to be evaluated in the CO-PROX reaction: (1) cerium-zirconium mixed oxide support (CeZr), (2) gold on cerium–zirconium mixed oxide (Au/CeZr), (3) impregnated copper on cerium–zirconium mixed oxide (CuOx/CeZr), (4) copper incorporated into cerium–zirconium mixed oxide (CuCeZr), (5) bimetallic catalyst Au-CuOx with impregnated copper oxide (AuCuOx/CeZr) and (6) bimetallic catalyst Au-CuOx with incorporated copper (Au/CuCeZr)

Summary

Introduction

Proton Exchange Membrane Fuel Cells (PEMFC) are very interesting in portable applications, since they generate energy from hydrogen with high efficiency, reduced emissions and quick responses to charge changes (Salemme, Menna, Simeone and Volpicelli, 2010). The PEMFC have low tolerance to CO (10 ppm), due to the poisoning by CO adsorption on the cell Pt anode. For this reason and for the effect on the kinetic of oxidation, there is a limitation to expand their use (Cheng et al, 2007; Choudhary and Goodman, 2002; Ko et al, 2006). Several methods have been reported for carbon monoxide removal from the steam reforming stream, such as preferential oxidation of CO (CO-PROX), selective methanation of CO, and selective diffusion through membranes (Haryanto, Fernando, Murali and Adhikari, 2005; Manzolini and Tosti, 2008; Ocampo, Louis and Roger, 2009). Preferential oxidation of CO (CO-PROX) is the simplest and most direct and accessible method for removing CO (Avgouropoulos et al, 2002; Epling, Cheekatamarla and Lane, 2003)

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