Activity of $\gamma $-Al$_{2}$O$_{3}$-based Mn, Cu, and Co oxide nanocatalysts for selective catalytic reduction of nitric oxide with ammonia


Abstract: Our studies on the selective catalytic reduction of NO (SCR-deNO) properties of M/$\gamma $-Al$_{2}$O$_{3}$ (M = Mn, Co, Cu) nanocatalysts are presented. All catalysts were prepared by homogeneous deposition precipitation using urea as the precursor for the precipitating agent. The SCR activity followed the order Mn/$\gamma $-Al$_{2}$O$_{3} >$ Cu/$\gamma $-Al$_{2}$O$_{3} >$ Co/$\gamma $-Al$_{2}$O$_{3}$. The nanocatalysts were characterized with respect to their texture (N$_{2}$-BET), particle size (TEM), reducibility (H$_{2}$-TPR), and acidity (NH$_{3}$-TPD). The TEM analysis revealed that the metal species have superior dispersion with less agglomeration and sintering on $\gamma $-Al$_{2}$O$_{3}$ support. The H$_{2}$-TPR results confirmed that the Mn/$\gamma $-Al$_{2}$O$_{3}$ nanocatalyst contains various oxidation states of manganese, which is useful for the catalyst to maintain the DeNO activities. The NH$_{3}$-TPD studies indicated that the addition of transition metal can significantly increase the surface acidity and Mn/$\gamma $-Al$_{2}$O$_{3}$ showed the most adsorbed sites of NH$_{3}$. Characterization results indicated that the acidity and the redox properties of the catalyst play important roles in the final catalytic activity in the SCR-NO process.

Keywords: NO, NH$_{3}$-SCR, transition metals, $\gamma $-Al$_{2}$O$_{3}$, nanocatalyst

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