Temperature programmed decomposition (TPDE) of [Mo(CO)6] on metal oxide supports: A novel tool to elucidate surface acidity and surface-mediated reactions

Abstract

A novel technique, the temperature programmed decomposition (TPDE) of [Mo(CO)6], has been developed to examine surface acid/base properties. In particular, the nucleophility of different surface hydroxyl groups can be quantified with this method, and it is found that the activation energy for decarbonylation of the carbonyl complex correlates well with the field strength of the metal cations in the support. Activation energies are derived from the CO peak maxima in the TPDE spectra by means of the Redhead equation. TPDE is also used to probe surface-mediated reactions of metal carbonyls. The technique enables identification of intermediates formed during the thermal decomposition process. Comparison with simulated TPDE spectra provides evidence for cluster formation during decarbonylation. By quantifying the amounts of CO and H2 generated during the TPDE reaction, the surface concentration of the adsorbed species and the oxidation state of the central atom can be deduced at any given temperature.