Applied Catalysis B: Environmental, Vol.26, No.2, 101-118, 2000
TPD, TPR and DRIFTS studies of adsorption and reduction of NO on La2O3 dispersed on Al2O3
The surface properties of La2O3 supported on gamma-Al2O3, as characterized by DRIFTS or temperature-programmed desorption (TPD), showed features more and more similar to unsupported La2O3 as the La2O3 loading increased. Optimum rates (mole/s g) were obtained when the bulk-like La2O3 surface area was maximized, and the 40% La2O3/Al2O3 catalyst had a rate high enough to possibly allow its use in combined-cycle power plants. TPD with La2O3/gamma-Al2O3 and pure gamma-Al2O3 after exposure to NO at 300 K gave three NO desorption peaks and the only O-2 desorbed coincided with the high-temperature NO peak near 800 K. TPD after (NO)-N-15-O-16 adsorption on O-18-exchanged La2O3/gamma-Al2O3 and gamma-Al2O3 surfaces showed that a very small amount of (NO)-N-15-O-18 desorbed from the middle-temperature sites near 700 K, while (NO)-N-15-O-18 and (OO)-O-16-O-18 desorbed from the high-temperature sites. Adsorption of NO on supported La2O3 resulted in the formation of nitrosyl, nitrite and nitrate species, and their thermal stabilities increased in the following order: NOdelta+ (on Al2O3)approximate to bridged nitrate (on La2O3)