A comparison between photocatalytic and catalytic oxidation of 2-Propanol over Au/TiO2-CeO2 catalysts

Photocatalytic and catalytic oxidation of 2-propanol, representative of volatile organic compounds (VOC's), were compared over mixed TiO2-CeO2-based catalysts. The effect of different amounts of CeO2 and the presence of gold (1 wt%) on TiO2 was investigated. In the photocatalytic oxidation CeO2 had a negative effect on the performance towards the alcohol conversion of both TiO2-CeO2 and Au/TiO2-CeO2 catalysts, being Au/TiO2 the most active system. On the contrary mixed TiO2-CeO2 and Au/TiO2-CeO2 samples showed a higher catalytic oxidation efficiency for 2-propanol conversion compared to the single oxides. In this case Au/CeO2 catalyst had the best performance. On the basis of characterization data (XRD, Raman spectroscopy, EDX, BET Surface area determinations, H2-TPR, DRIFT and DRS), it was proposed that the interaction of gold with TiO2 caused an enhancement of the partial photo-oxidation activity to acetone due to an increase of the charge separation between the excited electron and the hole of TiO2, whereas the coexistence of gold and both TiO2 and CeO2 oxides favoured the total oxidation of the alcohol to CO2. The catalytic oxidation of 2-propanol is, instead, mainly directed by the presence of a reducible oxide support as CeO2, necessary to enable a strong interaction with gold nanoparticles, providing very active lattice oxygen atoms.