Influence of the preparation of Au/Al2O3 on CH4 oxidation activity

Four different Au/Al2O3 catalysts were prepared via impregnation and deposi tion precipitation. The preparation technique used was found to have a larg e influence on the average Au particle size and amounts of Au adsorbed. For CH4 oxidation a clear particle size effect was observed, in which small Au particles are beneficial for high activity. From the preparation methods s tudied, homogeneous deposition precipitation leads to the smallest average particle size (3-5 nm) and, hence, to the most active catalysts. These cata lysts, however, showed some sintering of Au accompanied by a slight deactiv ation during catalytic reaction. The results do not support the idea of ion ic Au being responsible for the catalytic activity. (C) 2000 Academic Press .