Jeong Kwon Suh

Characterization of transition metal-impregnated LaAl complex oxides for catalytic combustion

Abstract The effects of transition metals on Laue5f8Al complex oxide support were investigated 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 were investigated by methane combustion. Increasing the calcination temperature from 1000 to 1600°C resulted in the crystallization of each Laue5f8Al complex oxide from an amorphous form to the La-β-Al2O3 phase of a layered structure. During calcination, the addition of chromium retarded the crystallization of the support. However, the addition of copper to the Laue5f8Al complex oxide accelerated the crystallization of the support. The Cr-impregnated Laue5f8Al complex oxide retained a large surface area of 10 m2/g even after calcination at 1400°C. However, the surface area of the Cu-impregnated Laue5f8Al complex oxide decreased abruptly to 1 m2/g after calcination at 1400°C. The surface composition of chromium did not change significantly with increasing calcination temperature. However, the surface composition of copper decreased gradually with increasing calcination temperature, implying the formation of a solid solution with the Laue5f8Al complex oxide. Whereas the catalytic acitivity of the Cu-impregnated Laue5f8Al complex oxide decreased abruptly with increasing calcination temperature, most of the catalytic activity of Cr-impregnated Laue5f8Al complex oxide was maintained after calcination at 1400°C.