The co-adsorption of hydrogen and carbon dioxide on catalysis

Abstract

In the elucidation of the reaction mechanism of a catalytic process it is important to establish the reaction intermediates and their possible role in the reaction. In most cases, however, this is not an easy task as a real reaction intermediate exists only transitorily and in a very low concentration on the catalysts. The adsorption of CO2 and the co-adsorption of H2 + CO2 on Re supported by Al2O3, TiO2, MgO and SiO2 have been investigated by FT-IR spectroscopy. The dissociation of CO2 was not experienced on the Re/Al2O3 reduced at 673 K, it occurred, however, on the sample reduced at 1073 K. Addition of H2 to CO2, initiated the dissociation on all catalysts as indicated by CO bands at 2022-2053 cm-1 . Besides, new spectral features were developed at 1600-1550, 1395 and 1365 cm-1 attributed to format species. No bands due to format were detected on Re/SiO2 and no format was detected following the co-adsorption of CO2-containing gas mixture on the supporting oxides alone. It was assumed that the format species identified in the surface interactions is located on the support, where it is stabilized. The possible pathways of the occurrence of format complex on the oxides are described.