XPS study of copper dispersion in CuO/Al2O3 catalysts

A series of CuO/Al2O3 catalysts with different Cu loading (3–15 wt % Cu) have been studied by XPS, to analyse the quantitative and qualitative changes occurring during the reductive pretreatment. In all the analysed samples CuO is reduced to Cu(O) and a decrease of the Cu/Al signal intensity ratio is observed. We have calculated the size of the Cu particles, for cubic and hemispheric shape by the comparison of the Cu/Al intensity ratio in reduced samples with the ratios in the corresponding untreated systems. A progressive linear increase of the size of the particles, as function of copper loading, is observed. The copper dispersion obtained by XPS data is in good agreement with the Cu surface area measured by NO adsorption, when the hemispheric shape of the Cu particles is considered.