In situ spectroscopic studies of methane catalytic combustion over Co, Ce, and Pd mixed oxides deposited on a steel surface

This study is an approach to resolve the mechanism of methane catalytic combustion over a series of palladium and cobalt palladium and ceria-doped catalysts supported on γ-Al2O3. The first and most important question addressed is whether methane adsorbs on the surface of the catalyst. Another task was to determine the stable intermediate products of methane oxidation. The main method used for both was in situ Diffuse Reflectance Infrared Spectroscopy (DRIFT) aided with Raman and X-ray Fluorescence spectroscopies. The main conclusions drawn from the results are that methane adsorbs only on the catalyst surface with pre-adsorbed oxygen, forming methoxy species on catalysts containing Pd, which has been confirmed by pulse in situ DRIFT experiments. During methane oxidation traced down by DRIFT, formates and carbonates (mono and free carbonates) are the stable intermediate products on catalysts containing Pd. Based on the in situ results and the literature data, the mechanism of methane catalytic combustion has been proposed, assuming one type of active centre.