TRUE AND SPECTATOR INTERMEDIATES IN CATALYSIS - THE CASE OF ETHANOL OXIDATION ON MOLYBDENUM OXIDE AS OBSERVED BY IN-SITU LASER RAMAN-SPECTROSCOPY

A high-throughput laser Raman spectrometer is used to detect adsorbed ethoxide species during the catalytic oxidation of ethanol over suppor ted molybdenum oxide at atmospheric pressure. Two different species ar e observed, a true reaction intermediate and a relatively inert specta tor on the surface. Steady-state and dynamic experiments indicate that the reactive species is associated with Mo=O terminal bonds on the su rface, while the spectator is associated with Mo-O-Mo bridging bonds. Deuterium isotopic substitution experiments indicate that the active i ntermediate is formed in an equilibrated adsorption step, and decompos es by a rate-determining alpha-C-H bond-breaking step to form acetalde hyde.