Co-precipitated copper zinc oxide catalysts for ambient temperature carbon monoxide oxidation: effect of precipitate ageing on catalyst activity

Abstract

A detailed study of the morphological changes that occur during the ageing of a copper zinc oxide (Cu ∶ Zn 2 ∶ 1), formed by co-precipitation from the nitrates is reported and discussed. Using TEM and STEM-EDS, the composition and morphology of the non-calcined precursor are observed to change from an initial amorphous state to micro-crystalline aurichalcite and rosasite, which are present as needles and platelets, respectively. In addition, the detailed microscopy study has shown that a dispersion of Cu-rich nanoparticles is progressively formed as the precipitate ages. On calcination at 550 °C, an intimate mixture of CuO and ZnO crystallites is formed, and using STEM-EDS analysis it is shown that the CuO contains Zn, and the ZnO contains Cu in solid solution. The highest incorporation of Zn into CuO correlates with the highest concentration of the Cu-rich nanoparticles in the precursor. The catalytic activity of the calcined copper zinc oxide is also correlated with the highest incorporation of Zn into CuO for the oxidation of carbon monoxide at 20 °C.