CuO–SiO 2 catalysts were prepared by the sol–gel technique and calcined at two temperatures, 673 and 1073 K. Characterization of the catalysts was achieved by BET, FTIR, TPR, dissociative N 2 O adsorption, XPS, HRTEM, and reactivity toward NO+H 2 . As a function of the calcination temperature, characterization techniques showed: textural (BET), morphological and structural (HRTEM), reducibility (TPR, XPS), dispersion, and catalytic reactivity (NO+H 2 ) differences between samples. Both samples showed remarkable stability during on-stream experiments. The microstructure of the catalysts as a consequence of the preparation method allows the understanding of the catalytic behavior of calcined and reduced samples as well as the stability toward sintering.