Gold supported on metal oxides for volatile organic compounds total oxidation

Abstract

Au was loaded (1wt.%) on different commercial oxide supports (CuO, Fe2O3, La2O3, MgO, NiO, Y2O3) by a double impregnation method (DIM). Samples were characterised by N2 adsorption at −196°C, scanning electron microscopy, high-resolution transmission electron microscopy, selected area electron diffraction, energy dispersive X-ray spectrometry, high-angle annular dark-field imaging (Z-contrast), X-ray diffraction and temperature programmed reduction. The materials were tested for the total oxidation of two volatile organic compounds: ethyl acetate and toluene. Toluene was more difficult to oxidise than ethyl acetate. Gold loaded on CuO and NiO yielded the best catalysts, although there was a larger increase in catalytic activity upon gold loading for less active oxides like MgO and Y2O3. The oxidation state of gold does not seem to play a significant role in the catalytic activity, with the exception of Au/Y2O3 where Au3+ was detected, leading to a decrease in the activity. The catalytic activity seems to be related with the reducibility of the support and the gold nanoparticle size, following a Mars-van Krevelen type of mechanism. The role of gold is to enhance the reducibility and reactivity of the surface of the oxide support and to increase the exchange rate between lattice and surface oxygen.