TEMPERATURE-PROGRAMMED OXIDATION OF CU/ZNO CATALYSTS WITH N2O - AN ATTEMPT FOR CHARACTERIZATION OF COPPER-CATALYSTS

For characterization of the surface structure of metallic copper formed on the support, temperature programmed oxidation (TPO) with N2O was carried out over various Cu/ ZnO catalysts. Four peaks of the N2 formation (alpha, beta, gamma and delta) were observed at 223, 400, 545 and 600 K in the TPO runs. The average copper crystallite size estimated from the sum of the amount of alpha- and beta-peaks agreed fairly with those determined by X-ray diffraction and transmission electron microscopy. It was concluded that alpha- and beta-peaks resulted from the oxidation of metallic copper atoms on the steps, comers and/or defect sites, and on the flat sites of the surface of copper crystallites, respectively, while gamma- and delta-peaks resulted from the bulk oxidation of copper.