Gold versus platinum on ceria–zirconia mixed oxides in oxidation of ethanol and toluene

The Ce–Zr mixed oxides have been examined as supports for platinum and gold in oxidation of ethanol and toluene. A weight ratio of Ce/Zr in the synthesized supports was 1/1. Two supported noble metals with a different loading (2.5 and 0.3 wt.%) were compared to each other as well as to selected industrial catalysts (HHC-5557 and VOC-1544). Whatever the metal content was, Pt catalysts were always more active in oxidation of ethanol and toluene than Au catalysts. Better reductive capability of platinum was confirmed by H2-TPR profiles and a higher activity of platinum may also be linked to changes in surface basic properties (a higher amount of basic centers) illustrated by CO2-TPD profiles. Deposition of gold on Ce–Zr mixed oxide resulted in a formation of certain amounts of crystalline Au phase detected by X-ray diffraction while the deposition of platinum did not produce any crystalline Pt phase. As observed by FE-SEM, part of Au was well dispersed but significant amount of Au was present as inactive crystals. Platinum catalysts were comparable or even more active than industrial catalysts (50% conversion of ethanol was achieved with 2.5Pt/CeZr(1) at 99 °C). On the other hand, gold catalysts proved the best selectivity in oxidation of ethanol.