The influence of cooling atmosphere after reduction on the catalytic properties of Au/Al2O3 and Au/MgO catalysts in CO oxidation Original Research Article

Unexpected activity alterations were observed in CO oxidation upon changing the atmosphere of cooling from an inert gas to hydrogen after reduction in hydrogen at 350 °C. Different supports resulted in different trends, e.g. over Au/MgO higher activities were obtained after cooling in helium, while Au/Al2O3 showed the opposite effect, i.e., higher activities were measured after cooling in hydrogen. The higher the Au content of the catalyst the more pronounced the “cooling effect”. Contrary to pure Au/Al2O3 catalysts the addition of redox-type modifiers, such as iron, manganese and cobalt to the support, the cooling in hydrogen decreased the activity. In situ FTIR results indicated that cooling in hydrogen increases the negative charge on the supported gold nanoparticles on both supports.