Self‐sustained oscillations within the temperature hysteresis in CO oxidation over Pd: Mathematical model of a cascade of continuous stirred‐tank reactors

Abstract

The results of temperature‐programmed reaction experimental studies and mathematical modeling of self‐sustained oscillations within an inverse temperature hysteresis in CO oxidation over Pd catalyst are presented. The experimental data demonstrate the influence of the reaction medium on the catalyst activity under reaction conditions. Under oxygen excess in the feeding gas mixture and high temperature, the defects appeared on the initially flat surface of metallic palladium due to deep oxidation of palladium (three‐dimensional PdO nanoparticles were observed). The palladium oxide reduced under cooling of the catalytic system, and the catalyst surface became flat again. To take into account these variations of the palladium surface structure, we consider the piecewise‐constant dependence of the rate constant of some reaction step on the concentrations of oxygen species, namely, the dissolved oxygen or oxide in the palladium bulk. The proposed model of the process in the cascade of continuous stirred‐tank reactors that account for these dependences qualitatively describes the inverse temperature hysteresis as well as the oscillatory dynamics within the hysteresis loop which were obtained experimentally.

Studies on High-Temperature Evolution of Low-Loaded Pd Three-Way Catalysts Prepared by Laser Electrodispersion

“…In the case of supported palladium, direct hysteresis is often observed [83][84][85][86][87]. However, Lashina et al reported an inverse hysteresis on palladium foil due to transformations between metallic Pd and bulk PdO taking place during the heating/cooling cycles [82,88]. The appearance of the inverse hysteresis in the case of the Pd/A catalyst can be attributed to a similar phenomenon.…”