Structure and Reduction and Mixed Copper-Aluminum Oxide

Abstract

Mixed oxides of copper and aluminum were prepared in porous form by the citrate process under various calcination conditions. The oxide samples were characterized by several techniques to determine chemical structure and texture. Atomic absorption spectroscopy provided the fractions of copper soluble and insoluble in hot nitric acid, which closely corresponded to CuO and CuAl_2O_4, respectively. X-ray diffraction (XRD) provided complementary information about the content of the pure and compound oxides. X-ray line broadening, scanning electron microscopy, and transmission electron microscopy were used to estimate the size of crystallites or phase domains. The reduction by hydrogen of samples containing different amounts of CuO and CuAl_2O_4 was studied by thermogravimetric analysis and XRD. The compound oxide CuAl_2O_4 and part of CuO closely associated with Al_2O_3 were reduced much more slowly than bulk CuO. Oxides of 1+ oxidation state, Cu_2O and CuAlO_2, were identified as reduction intermediates.

Additional details