M. Haneda et al., Surface characterization of alumina-supported catalysts prepared by sol-gel method. Part II. Surface reactivity with CO, PHYS CHEM P, 3(7), 2001, pp. 1371-1375
Surface reactivity toward H-2 and CO using a pulse method was investigated
for Al2O3, In2O3-Al2O3 and Ga2O3-Al2O3. It was found that reduction by eith
er CO or H-2 and reoxidation by O-2 occurred reversibly on In2O3-Al2O3. Alt
hough the surface of Ga2O3-Al2O3 was hardly reduced by H-2, CO consumption
and CO2 formation was observed on exposure to CO. Mass spectroscopic analys
is revealed the formation of H-2 from injection of CO pulses on Ga2O3-Al2O3
, while small amounts of H-2 were detected on In2O3-Al2O3. The formation of
H-2 on Ga2O3-Al2O3 was also evidenced by Fourier transform infrared (FT-IR
) spectroscopy. Namely, when Ga2O3-Al2O3 was exposed to CO at elevated temp
eratures above 573 K, the IR band assignable to Gay+-H species was detected
at 1997 cm(-1). A reaction model in which the reaction of CO with basic hy
droxy groups occurs on the surface of Ga2O3-Al2O3 (CO+OH --> CO2+1/2H(2)) i
s proposed.