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

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.