The effects of transition metals on La-A1 complex oxide support were i
nvestigated in order to develop a high-temperature combustion catalyst
. The properties of the catalysts were examined by X-ray diffraction (
XRD), electron spectroscopy for chemical analysis (ESCA), temperature-
programmed reduction (TPR), and BET. The activities of the catalysts w
ere investigated by methane combustion. Increasing the calcination tem
perature from 1000 to 1600 degrees C resulted in the crystallization o
f each La-A1 complex oxide from an amorphous form to the La-beta-Al2O3
phase of a layered structure. During calcination, the addition of chr
omium retarded the crystallization of the support. However, the additi
on of copper to the La-A1 complex oxide accelerated the crystallizatio
n of the support. The Cr-impregnated La-Al complex oxide retained a la
rge surface area of 10 m(2)/g even after calcination at 1400 degrees C
. However, the surface area of the Cu-impregnated La-A1 complex oxide
decreased abruptly to 1 m(2)/g after calcination at 1400 degrees C. Th
e surface composition of chromium did not change significantly with in
creasing calcination temperature. However, the surface composition of
copper decreased gradually with increasing calcination temperature, im
plying the formation of a solid solution with the La-A1 complex oxide.
Whereas the catalytic activity of the Cu-imprepnated La-A1 complex ox
ide decreased abruptly with increasing calcination temperature, most o
f the catalytic activity of Cr-impregnated La-A1 complex oxide was mai
ntained after calcination at 1400 degrees C.