N2O decomposition over K-promoted Co-Al catalysts prepared from hydrotalcite-like precursors

N2O decomposition was investigated over a series of K-promoted Co-Al catalysts. The activity tests showed that doping with K greatly enhanced the catalytic activity of the Co-Al catalyst, and the enhancement was critically dependent on the amount of K and the calcination temperature. When the catalyst had a K/Co atomic ratio of 0.04 and was calcined at 700-800 degrees C, a full N2O conversion could be reached at a reaction temperature of 300 degrees C. Moreover, even under the simultaneous presence of 4% O-2 and 2.6% water vapor, such high-temperature treated K/Co-Al catalyst exhibited high reactivity and stability, with the N2O conversion remaining at a constant value of 92% over 40 h run at 360 degrees C. In contrast, non-doped Co-Al catalyst showed a severe activity loss under such reaction conditions. A combination of characterization techniques was employed to reveal the promoting role of K and the effect of calcination temperature. The results suggest that doping with K increases the electron density of Co and weakens the Co-O bond, thus promoting the activation of N2O on the Co sites and facilitating the desorption of oxygen from the catalyst surface. High-temperature calcinations made the desorption of O-2 proceed more readily. (C) 2008 Elsevier B.V. All rights reserved.