Activity, Selectivity, and Long-Term Stability of Different Metal Oxide Supported Gold Catalysts for the Preferential CO Oxidation in H2-Rich Gas

A comparative study of the catalytic performance and long-term stability of various metal oxide supported gold catalysts during preferential CO oxidation at 80°C in a H2-containing atmosphere (PROX) reveals significant support effects. Compared to Au/γ-Al2O3, where the support is believed to behave neutrally in the reaction process, catalysts supported on reducible transition metal oxides, such as Fe2O3, CeO2, or TiO2, exhibit a CO oxidation activity of up to one magnitude higher at comparable gold particle sizes. The selectivity is also found to strongly depend on the employed metal oxide, amounting, e.g., up to 75% for Au/Co3O4 and down to 35% over Au/SnO2. The deactivation, which is observed for all samples with increasing time on stream, except for Au/γ-Al2O3, is related to the build-up of surface carbonate species. The long-term stability of the investigated catalysts in simulated methanol reformate depends crucially on the ability to form such by-products, with magnesia and Co3O4 supported catalysts being most negatively affected. Overall, Au/CeO2 and, in particular, Au/α-Fe2O3 represent the best compromise under the applied reaction conditions, especially due to the superior activity and the easily reversible deactivation of the latter catalyst.