L. Dong et al., DISPERSION AND REDUCTION BEHAVIOR OF CUO ALPHA-FE2O3 SYSTEMS/, Journal of the Chemical Society. Faraday transactions (Print), 94(19), 1998, pp. 3033-3038
Citations number
29
Categorie Soggetti
Chemistry Physical","Physics, Atomic, Molecular & Chemical
The dispersion and reduction behaviors of CuO/alpha-Fe2O3 samples have
been studied by using X-ray diffraction (XRD), X-ray photoelectron sp
ectroscopy (XPS), Brunauer-Emmett-Teller (BET) and temperature program
med reduction (TPR). XRD and XPS results show that the dispersion capa
city of CuO on alpha-Fe2O3 is about 13.7 Cu2+ nm(-2) (alpha-Fe2O3). At
low copper loading, highly dispersed surface copper oxide is the main
species, and crystalline CuO evidently appears after the Cu loading e
xceeds the dispersion capacity. For Cu XPS spectra, the intensity rati
o of satellite peaks (I-sat) to the principal peaks (I-pp) shows that
the highly dispersed Cu2+ ions simultaneously exist as tetrahedrally a
nd octahedrally coordinated states in the low Cu loading samples, and
the octahedrally coordinated surface Cu species is the predominant spe
cies in high Cu loading samples, which is in basic agreement with the
prediction of the incorporation model proposed previously (Y. Chen and
L. F. Zhang, Catal. Lett., 1992, 12, 51). The BET surface area of alp
ha-Fe2O3 support in all the samples remains constant, indicating that
the calcination process has not induced an evident change to the surfa
ce of alpha-Fe2O3 support. TPR results indicate that the reduction pea
ks at about 473 and 493 K correspond to the reduction of the octahedra
lly and tetrahedrally coordinated surface copper oxide species, respec
tively, and the reduction peak at about 563 K is ascribed to the reduc
tion of crystalline CuO. In addition, the influence of the different c
alcination temperatures on the interaction between CuO and alpha-Fe2O3
has also been investigated by XRD, TPR and XPS, and the results show
that the calcination temperature can affect the extent of interaction,
and a new compound, CuFe2O4, formed as the CuO/alpha-Fe2O3 sample was
calcined at 1123 K.