A Remarkable Catalyst Combination to Widen the Operating Temperature Window of the Selective Catalytic Reduction of NO by NH3

On the basis of the idea of combining high selective catalytic reduction (SCR) activity, high N-2 selectivity, and broad operating temperature window, we developed a combined catalyst process that was found to be a convenient way to design a highly efficient SCR process for NO with NH3. The single catalysts of MnOx-CeO2/TiO2 and V2O5-WO3/TiO2 as well as combined catalysts with different configurations were fully characterized by XRD, temperature-programmed reduction of H-2, and temperature-programmed desorption of NO/O-2. In addition, they were tested for the oxidation of NO or NH3 as well as the SCR of NO with NH3. The correlations between combining configurations and SCR activity results were also revealed. Furthermore, fundamental evidences were given for the rational design of the process and its efficiency maximization (assembly order and catalytic bed volume). An adequate configuration, with MnOx-CeO2/TiO2 and V2O5-WO3/TiO2 active materials, ensures an excellent SCR performance (NO conversion >85%, N-2 yield >70%, and decreased N2O production) over a wide operating temperature window (from 150 to 400 degrees C).