Influence of H2, CO2 and H2O on the activity and deactivation behavior of Au/CeO2 catalysts in the water gas shift reaction at 300 °C

The effect of H2, CO2 and H2O on the activity, stability and deactivation behavior of an oxidatively (O400) and a reductively (H400) pretreated 4.5 wt.% Au/CeO2 catalyst in the water gas shift (WGS) reaction at 300 °C was studied by kinetic and spectroscopic measurements, using different gas mixtures, going stepwise from idealized to a semi-realistic reaction atmosphere. The results were compared with data for the WGS reaction determined under similar reaction conditions at a lower reaction temperature of 180 °C [Y. Denkwitz, A. Karpenko, V. Plzak, R. Leppelt, B. Schumacher, R.J. Behm, J. Catal. 246 (2007) 74]. The formation/removal of adsorbed reaction intermediates and side products (surface carbonates, formates, OHad, COad) was followed by in situ IR spectroscopy (DRIFTS). Variation of the reaction gas mixture led to significant effects on the initial activity and the stability of the catalysts, which depend also on the pre-treatment of the catalysts. The resulting trends are compared with those obtained for reaction at 180 °C, consequences for the reaction mechanism and for applications in fuel gas processing at medium temperatures will be discussed.