Preferential CO oxidation over nanosized gold catalysts supported on ceria and amorphous ceria-alumina
Résumé
1 wt.% Au supported on CeO2-Al2O3 (Ce/Ce + Al: 0, 2, 5, 10, 15, and 20 mol%) was prepared by impregnation in organic medium of high-surface area supports prepared by Evaporation Induced Self Assembly (EISA) route. For comparison, a 1 wt.% Au/CeO2 was also prepared using a commercial support. All the prepared catalysts present a BET surface area roughly between 200 and 340 m2 g−1. The reducibility, the oxygen storage capacity (OSC) and the oxygen mobility determined by oxygen isotopic exchange (OIE) of the 1 wt.% Au/CeO2-Al2O3 are enhanced by the presence of gold and increases with the cerium content in the support. The values of the OSC and the oxygen mobility in the Au/CeO2-Al2O3 catalysts with high cerium loading are higher than those determined on their Au/CeO2 counterpart. The activity in CO oxidation of the Au/CeO2-Al2O3 catalysts increases with the cerium content in the support, which could be linked to the better oxygen mobility of these systems, whereas in CO-PrOx the Au/CeO2-Al2O3 catalysts with medium cerium loading (Ce/Ce + Al = 5 and 10 mol%) present the highest CO conversion at 50-60 °C. The catalysts are stable at 100 °C in CO + O2 + H2 mixtures. The addition of CO2 in the stream strongly deactivates Au/CeO2, whereas Au/CeO2-Al2O3 is less affected. Whatever the catalyst, the presence of steam has no significant effect on the catalytic performances.