Adsorption and decomposition of ethanol on supported Au catalysts

The adsorption and reactions of ethanol are investigated on Au nanoparticles supported by various oxides and carbon Norit. The catalysts are characterized by means of XPS. Infrared spectroscopic studies reveal the dissociation of ethanol to ethoxy species at 300 K on all the oxidic supports. The role of Au is manifested in the enhanced formation of ethoxy species on Au/SiO2, and in increased amounts of desorbed products in the TPD spectra. The supported Au particles mainly catalyse the dehydrogenation of ethanol, to produce hydrogen and acetaldehyde. An exception is Au/Al2O3, where the main process is dehydration to yield ethylene and dimethyl ether. C–C bond cleavage occurs to only a limited extent on all samples. As regards to the production of hydrogen, the most effective catalyst is Au/CeO2, followed by Au/SiO2, Au/Norit, Au/TiO2 and Au/MgO. A fraction of acetaldehyde formed in the primary process on Au/CeO2 is converted above 623 K into 2-pentanone and 3-penten-2-one. The decomposition of ethanol on Au/CeO2 follows first-order kinetics. The activation energy of this process is 57.0 kJ/mol. No deactivation of Au/CeO2 is observed during ∼10 h at 623 K. It is assumed that the interface between Au and partially reduced CeO2 is responsible for the high activity of the Au/CeO2 catalyst.