CHARACTERIZATION OF TRANSITION METAL-IMPREGNATED LA-AL COMPLEX OXIDESFOR CATALYTIC COMBUSTION

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.