Influence of ferric oxide modification on the properties of copper oxide supported on gamma-alumina.

X-ray diffraction (XRD), Mössbauer spectroscopy, and temperature-programmed reduction (TPR) were employed to investigate the dispersion and reduction behaviors of the Fe(2)O(3)/CuO/gamma-Al(2)O(3) system. The results indicated that: (1) the crystalline CuO particle in the CuO/gamma-Al(2)O(3) samples was redispersed during impregnating CuO/gamma-Al(2)O(3) samples with Fe(NO(3))(3) solutions; (2) two different dispersion states of surface iron species could be observed, i.e., State I corresponding to the iron(III) species located in the D layer on the surface of gamma-Al(2)O(3) and State II corresponding to those in the C layer. The dispersed states of surface iron(III) species were closely related to the iron loading amount; (3) the copper species located in the D layer of alumina surface was easily reduced and the copper species located in the C layer were more stable, which could be due to the influence of the iron(III) species in the different layers; (4) in the NO+CO reaction, the catalytic performances were enhanced due to the Cu-Fe synergism and the main active species in this system should be the surface-dispersed copper oxide species.