TPR and XRD studies of yttria-doped ceria/γ-alumina-supported copper oxide catalyst Original Research Article

Yttria-doped ceria (YDC) and pure ceria (CeO2), respectively, were deposited on γ-alumina (γ-Al2O3) using the impregnation method; then, copper oxide was also supported on them by employing the impregnation method. For comparison, CuO/γ-Al2O3 catalysts were prepared in this work. The catalysts were characterized by temperature-programmed reduction (TPR) and X-ray diffraction (XRD). For CuO/γ-Al2O3 catalysts, two TPR peaks, namely β and γ, were observed. These have been attributed to the reduction of highly dispersed copper oxide species and bulk-like copper oxide, respectively. For CuO/CeO2/γ-Al2O3 and CuO/YDC/γ-Al2O3 catalysts, four TPR peaks, namely α1, α2, β′ and γ′, could be observed. The α peaks with lower peak temperatures as compared to those of β′ and γ′ peaks have been attributed to the reduction of interface-boundary copper oxide species that contact closely and interact strongly with the supported ceria or YDC. Crystal sizes calculated from XRD measurements confirmed that yttria (Y2O3) addition could lead to crystal growth of ceria and correspondingly enhance the dispersion of the supported copper oxide due to the partition of YDC crystallite. Hence, this work shows that supported YDC and ceria can act bi-functionally as a textural promoter as well as a structural promoter.