Activity, stability, and deactivation behavior of supported Au/TiO2 catalysts in the CO oxidation and preferential CO oxidation reaction at elevated temperatures

The influence of elevated reaction temperatures on the activity, long-time stability, and deactivation behavior of Au/TiO2 catalysts for CO oxidation was studied by kinetic and in situ IR measurements in the temperature range 80–180 °C, both in an idealized, H2-free reaction atmosphere and in a H2-rich gas mixture. The results are discussed in a molecular picture. Most important for practical applications (PROX reaction), the selectivity for CO oxidation in H2-rich gas mixtures decreases sharply with increasing temperature, from ∼60% at 80 °C to ∼15% at 180 °C. The increasing tendency for H2 oxidation is reflected also by a distinctly lower apparent activation energy for CO oxidation in the presence of H2 (18 ± 3 kJ mol−1) compared to reaction in a H2-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.

Graphical abstractThe mechanisms governing the oxidation of CO on Au/TiO2 catalysts, both in the absence of H2 and in H2-rich gas mixtures, the deactivation behavior and the apparent activation barrier for CO oxidation over these catalysts at elevated temperatures, in the range 80–180 °C, were investigated. Distinct temperature effects were observed, they are discussed in a molecular picture.Figure optionsDownload full-size imageDownload high-quality image (108 K)Download as PowerPoint slide