Dispersion of copper oxide supported on γ-alumina and its sulfation properties

CuO/γ-Al ₂O ₃ catalysts were prepared by impregnation with different CuO loadings. The dispersion of CuO supported on γ-Al ₂O ₃ support was studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), and temperature programmed reduction (TPR). The dispersion threshold of CuO in γ-Al ₂O ₃ determined by X-ray quantitative analysis was 0.275 g/g, i.e., 0.275CuAl. Highly dispersed CuO or crystalline CuO would appear on the γ-Al ₂O ₃ support when CuO loading was below or more than its dispersion threshold. TPR experiments show that reduction peak temperature ranges of 0.1CuAl and pure CuO are 420-690 °C and 290-380 °C, respectively. 0.1CuAl is not easily reduced due to interaction between CuO and γ-Al ₂O ₃. 0.5CuAl shows a two-step reduction range during 210-300 °C and 410-730 °C, which confirms the existence of highly dispersed CuO and crystalline CuO. The sulfation experiments show the optimal CuO loading amount is far below its dispersion threshold, and copper oxide supported on γ-Al ₂O ₃ is in the form of submonolayer.