The role of ionic and cluster active centers of Pt/CeO2 catalysts in CO oxidation. Experimental study and mathematical modeling

Abstract

In this work, for the first time, the experimental catalytic kinetics of the CO oxidation reaction on platinum–ceria catalysts was simulated in a wide temperature range −50–450 °C. On the basis of the experiments performed, a substantiation of the catalytic action of two types of Pt-containing active centers in the form of isolated [Pt2+-O4] ions and PtOx clusters is presented. The relative content of these platinum forms on the ceria surface is controlled by the loading of platinum. Using the catalysts with a low content of platinum, where the active centers are isolated [Pt2+-O4] ions, a satisfactory simulation of CO conversion depending on temperature was carried out based on the concepts of the Mars-van Krevelen (MvK) mechanism. It was established that these centers provide the catalysts activity in the temperature range above 100 °C. To simulate the reaction kinetics in the temperature range below 100 °C, the Pt-O-Pt active centers based on PtOx cluster forms were considered. The PtOx cluster forms made it possible to consider both the MvK mechanism and temperature-dependent associative Low-T mechanism. The introduction into the kinetic scheme of stages simulating the implementation of both the Low-T and the MvK mechanisms allowed us to perform complete quantitative modeling of the experimental data over the entire temperature range of the reaction from −50 °C to 450 °C.