Role of support in the oxidation of acetylene over gold catalysts

The influence of the carrier (CeO2, TiO2 or ZrO2) on the reaction of acetylene oxidation over a 2% gold catalyst has been investigated in the presence or in the absence of CO. XPS reveals that gold is metallic in every case and the percentage of gold on the surface is always higher than that in the bulk confirming the wide dispersion as evaluated by TEM. There is a significant effect of the support on the activity in the absence of CO, but the presence of CO affects the reactivity differently according to the support. In a mixture of CO and C2H2, the oxidation of CO is systematically inhibited by C2H2 whereas the behaviour is completely different for the oxidation of C2H2. CO has no effect upon Au/CeO2, acts as an inhibitor with Au/TiO2 and as a promoter with Au/ZrO2. Kinetic study reveals that the order towards C2H2 remains unchanged whereas the order towards O2 clearly depends upon the support. These effects on activity and kinetics may result from various factors discussed in this paper.