Highly stable bimetallic Au–Cu supported on Al2O3 for selective CO oxidation in H2-rich gas: effects of Cu/Au atomic ratio and sensitive influence of particle size

Abstract

A series of bimetallic Au_xCu_y/Al₂O₃ (x/y = 3/1, 1/1 and 1/3) catalysts were prepared by direct anion exchange (DAE) and impregnation (IMP) methods and used for selective CO oxidation in H₂-rich gas. The influences of pretreatment processes such as calcination or reduction on the catalytic activity as well as the durability of these catalysts were investigated. With an increased atomic ratio of Au/Cu, the catalytic performance decreased for both calcined and reduced samples. However, if considering them with the same atomic ratio of Au/Cu in the second run at increasing reaction temperature, reduced bimetallic Au–Cu gave higher CO conversion and CO₂ yield and durability under the reaction stream. To reveal the reasons for high catalytic performance, a variety of characterization techniques were employed, e.g. XRD, XPS, TEM and FTIR. TEM results indicated that metal particle sizes in the case of the reduced catalysts were smaller than those of the calcined samples. The main reason resulting in the calcined catalyst deactivation could be ascribed to the presence of larger metal particles at relatively high reaction temperature.