Chromium oxide was supported on different commercial aluminas. Their charac
teristics were assessed by different techniques (X-ray diffraction, X-ray p
hotoelectron, laser Raman, and electron paramagnetic resonance spectroscopi
es, and Brunauer-Emmett-Teller surface, temperature-programmed reduction, a
nd temperature-programmed desorption measurements). The variation of the Cr
3+/Cr6+ ratio was accounted for by the interaction between the chromium pha
se and the support. The tendency of Cr3+ to form aggregates such as Cr2O3 w
as induced by the support. The features of the support exert-an influence u
pon chromium stabilization both in its oxidation states 6+ and 3+ and in th
e coordination of surface chromia species. The total acid sites and the oxi
dized chromium have a marked effect on activity and selectivity at initial
operation times.