Toluene total oxidation over CuO-CeO2/Al2O3: structural and kinetic characterization

Catalytic oxidation is an important technique for the destruction of Volatile Organic Compounds (VOCs). Precious metals, and the cheaper transition metal oxides constitute efficient catalysts for such processes. In this work, the total oxidation of toluene as VOC model molecule is studied over the binary metal oxide CuO-CeO2/gamma-Al2O3 using Temporal Analysis of Products (TAP). TAP is a transient pulse response technique with millisecond time resolution which help obtain information on the reactants, intermediates and end-products. Toluene reacts catalytically with oxygen to form CO2 and H2O, while oxygen in the feed re-oxidize the catalyst, according to the mechanism of Mars and van Krevelen. The TAP data allows to illustrate the reaction with a detailed reaction network. In order to elucidate the catalytic structure-activity relationship, the catalyst is characterized by high-resolution transmission electron microscope (HRTEM) and X-ray absorption spectroscopy (XAS). This results in the discovery of the active phase in the catalyst which is a solid solution of ceria with built-in substitutional Cu2+. The interaction between Ce and Cu herein, is responsible for the high reactivity of the bimetallic catalyst in the total oxidation of toluene. The reaction network and the structural information are finally coupled to a microkinetic model that describes the experimental data over a wide range of experimental conditions. Microkinetic modeling of the reaction using the transient response experimental data allows identification of the kinetically significant steps and estimation of the corresponding kinetic parameters