Selective CO Oxidation over Au Supported On Mixed Oxides: Effect of Preparation on Activity and Selectivity

Au/CeLaOx mixed oxide catalysts containing 0.5 to 1.0 wt% Au were prepared via coprecipitation with HAuCl4, the appropriate nitrate precursors, and either urea or Na2CO3 as the precipitant. BET surface area measurements for the Au/CeLaOx catalysts varied in the range of 16-107 m/g depending on the precipitant, aging time, and calcination conditions. The catalysts were tested for the selective oxidation of 1% CO in a stream containing 50% H2, at temperatures between 95°C and 150°C. Although the selectivities of the Au/CeLaOx catalysts were similar, the activity of the catalyst prepared with Na2CO3 was higher than the catalyst prepared with urea at low temperatures. The differences in the activity are ascribed to the differences in the metal loading and the Ce/La ratio in the catalysts, and the resultant effect on the reduction properties of the catalysts. When Na2CO3 was used as a precipitant, the catalysts did not require activation in H2, but did exhibit an induction period during the first 1.5 hours of reaction. Lower activity was observed for both the Na2CO3 and urea prepared catalysts without calcination.