Transient kinetic model of CO oxidation over a nanostructured Cu 0.1Ce 0.9O 2− y catalyst

Abstract

The oxidation of carbon monoxide under dynamic conditions was studied over a novel nanostructured Cu 0.1Ce 0.9O 2− y catalyst. CO temperature-programmed reduction provides a qualitative picture of the reducibility of that catalyst. Step-change experiments in CO concentration in the temperature range between 50 and 250 °C allowed us to estimate the oxygen storage capacity of the catalyst as a function of temperature. The measured CO and CO 2 responses were used to construct a detailed transient kinetic model based on elementary reaction steps. In the modeling, elementary reaction steps such as the adsorption of CO on oxidized and reduced catalyst active sites, diffusion of subsurface lattice oxygen to the surface, reoxidation of reduced catalyst active sites by the subsurface lattice oxygen, and the surface reaction of CO to CO 2 were considered. The calculated activation energies for various surface reaction steps were in the range from 9.7 to 39.6 kJ mol −1, for the catalyst reoxidation step 72.9 kJ mol −1, and for the lattice oxygen diffusion in the Cu 0.1Ce 0.9O 2− y catalyst 40.0 kJ mol −1. These values are discussed in detail. The bulk oxygen diffusion coefficient is equal to 3.2×10 −12 cm 2 s −1 at 250 °C. This value is in the range of bulk diffusion coefficients measured over other oxide catalysts.