Abstract :
Europium amide species prepared by dissolving Eu in a liquid ammonia were supported on alumina, and the samples
EurAl2O3. were evacuated at various temperatures. The samples exhibited the activity for the isomerization of
2,3-dimethylbut-1-ene to 2,3-dimethylbut-2-ene, and the catalytic activity changed remarkably with the evacuation tempera-
ture and the loading amount of Eu. X-ray absorption near edge structure XANES.spectra of the low loading 4 wt.%.and
high loading 8 wt.%.EurAl2O3 showed that Eu species in these samples are the mixture of Eu2q and Eu3q ions and the
composition of di- and trivalent ions changes with the evacuation temperature. Structural analyses by extended X-ray
absorption fine structure EXAFS.spectra indicated that Eu ions preferentially react with OH groups on an Al2O3 surface to
form the isolated Eu species in 4 wt.% EurAl2O3, while the additional Eu species consisting of the Eu atoms bridged by the
nitrogen atom are formed in 8 wt.% EurAl2O3. It has been revealed that the former Eu species is inactive for the
isomerization of 2,3-dimethylbut-1-ene, but the latter is active. These results were in good agreement with those obtained
from IR measurements. EXAFS analysis also clarified close relationship between the catalytic activity and the degree of the
aggregation of the active Eu species. q2000 Elsevier Science B.V. All rights reserved.
