Gold supported on surface acidity modified Y-type and iron/Y-type zeolite for CO oxidation

A modified method for the preparation of gold in Y-type zeolite was developed in this research. Prior to the preparation of gold catalysts, the surface property of the zeolite (with or without iron) was adjusted in a 1N sodium nitrate solution at pH 6. After drying, the zeolite was added into a chloroauric acid solution at pH 6 for gold loading. The resulted catalysts (i.e. Au/Y or Au/Fe/Y) possessed much better activity and stability for CO oxidation than those (i.e. Au/Y(NP) or Au/Fe/Y(NP)) without any surface pretreatment. Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) studies indicate that the gold particles in Au/Y are smaller and more uniformly distributed than those in Au/Y(NP). XPS and temperature-programmed reduction (TPR) results suggest the strong interaction between gold and iron in Y-type zeolite. Furthermore, it was found from this research that Au/Fe/Y had full initial activity for CO oxidation at 0°C and Au/Y required an induction period to reach a comparable activity to Au/Fe/Y. However, the stability of the activated Au/Y was much better than that of Au/Fe/Y. It can be concluded from XPS results that the formation of carbonate-like species, which covered the active sites for CO oxidation, was the main cause for the deactivation of Au/Fe/Y. On the other hand, TEM study suggests that the sintering of nano-gold particles was the main reason for the slight deactivation of Au/Y.