Low-temperature activity of Pd/CeO2 catalysts: Mechanism of CO interaction and mathematical modelling of TPR-CO kinetic data

• Mathematical model was proposed to describe CO interaction with Pd/CeO 2 catalysts. • Three types of active Pd species were introduced in model for detailed simulations. • Simulations describe TPR-CO kinetic curves for catalysts depending on calcination. • Role of Pd species for low temperature activity was established. • Oxygen flow from ceria to reduced Pd specifies the activity at higher temperatures. We studied the kinetic of CO interaction with Pd/CeO 2 catalysts during temperature programmed reactions (TPR-CO). Increasing of the calcination temperature leads to the changes of palladium states in the catalysts structure from solid solution to surface clusters and nanoparticles. Kinetic simulation showed that surface clusters are the most active species at temperatures below 100 °C. The blurry CO 2 evolution in the temperature range 100–250 °C is determined by the effect of bulk-surface transfer of lattice oxygen to the surface clusters. The separate sharp peak at 200 °C was simulated to be attributed to the reduction of the nanoparticles. In the high-temperature range of TPR-CO the reduced active centres on the surface of ceria are supplied with oxygen from the ceria bulk. Upon increasing the calcination temperature, the concentration of active oxygen in the ceria lattice taking part in the reaction with CO increases, and the catalyst is more reduced.