K. Shimizu et al., Spectroscopic characterisation of Cu-Al2O3 catalysts for selective catalytic reduction of NO with propene, PHYS CHEM P, 2(10), 2000, pp. 2435-2439
Copper-aluminium mixed oxide catalysts (Cu-Al2O3) for selective reduction o
f NO with propene (C3H6-SCR) were characterised as a function of Cu content
. The results from different techniques, Cu K-edge and Cu L-3-edge XANES, d
iffuse reflectance UV-Vis, XPS, and XRD were combined to develop coherent d
escription of the phases present and cation site distribution in Cu-Al2O3.
Both the bulk and the surface of Cu-Al2O3 consist of Cu2+ cations at tetrah
edral or octahedral sites of the Al2O3 matrix, forming an aluminate phase i
n a wide range of Cu content (1-30 wt.%). Cu L-3-edge XANES analysis succee
ded in quantifying the fraction of tetrahedral and octahedral Cu2+ ions; th
e fraction of octahedral Cu2+ decreased as Cu concentration increased. The
catalytic activity for C3H6-SCR per surface area of the catalysts increased
as surface Cu2+ concentration increased, indicating that Cu2+ ions in the
aluminate phase are responsible for the activity. The activity per surface
Cu2+ decreased as surface Cu2+ concentration increased, which coincides wit
h the decrease in the fraction of octahedra. The Cu2+ cations in octahedral
sites should be responsible for the higher intrinsic activity.