| Summary: | Manganese alumina composited oxides (MnAlO<i><sub>x</sub></i>) catalysts with ordered mesoporous structure prepared by evaporation-induced self-assembly (EISA) method was designed for the selective catalytic reduction (SCR) of NO<i><sub>x</sub></i> with NH<sub>3</sub> at low temperature. The effect of calcination temperature of MnAlO<i><sub>x</sub></i> catalysts was investigated systematically, and it was correlated with SCR activity. Results showed that with an increase in calcination temperature, the SCR activity of MnAlO<i><sub>x</sub></i> catalysts increased. When the calcination temperature was raised up to 800 °C, the NO<i><sub>x</sub></i> conversion was more than 90% in the operation temperature range of 150~240 °C. Through various characterization analysis, it was found that MnAlO<i><sub>x</sub></i>-800 °C catalysts possessed enhanced redox capacities as the higher content of Mn<sup>4+</sup>/(Mn<sup>3+</sup> + Mn<sup>4+</sup>). Moreover, the improved redox properties could contribute to a higher NO<i><sub>x</sub></i> adsorption and activation ability, which lead to higher SCR performance of MnAlO<i><sub>x</sub></i>-800 °C catalysts. In situ DRIFTs revealed that the adsorbed NO<sub>2</sub> and bidentate nitrate are the reactive intermediate species, and NH<sub>3</sub> species bonded to Lewis acid sites taken part in SCR progress. The SCR progress predominantly followed E–R mechanism, while L–H mechanism also takes effect to a certain degree.
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