Activity, stability, and deactivation behavior of supported Au/TiO 2 catalysts in the CO oxidation and preferential CO oxidation reaction at elevated temperatures

Abstract

The influence of elevated reaction temperatures on the activity, long-time stability, and deactivation behavior of Au/TiO 2 catalysts for CO oxidation was studied by kinetic and in situ IR measurements in the temperature range 80–180 °C, both in an idealized, H 2-free reaction atmosphere and in a H 2-rich gas mixture. The results are discussed in a molecular picture. Most important for practical applications (PROX reaction), the selectivity for CO oxidation in H 2-rich gas mixtures decreases sharply with increasing temperature, from ∼60% at 80 °C to ∼15% at 180 °C. The increasing tendency for H 2 oxidation is reflected also by a distinctly lower apparent activation energy for CO oxidation in the presence of H 2 (18 ± 3 kJ mol −1) compared to reaction in a H 2-free reaction mixture (30 ± 3 kJ mol −1). In all cases, carbonate formation is observed and proposed to contribute to the deactivation, but with different extents depending on the reaction conditions.