Distributions and Species of MnOx Included in MnOx/TiO2 Catalysts for Denitration at Low Temperature

MnOx/TiO2 catalysts are active and stable at low temperature, and it is appropriate for cement production to enforce NOx emissions. In this study, the denitration process was promoted by the transformation of a variety of MnOx forms in the SCR reaction. The efficiency and selectivity of catalysts depended on the form and dispersion degree of MnOx. By changing the precursors, calcination temperatures, synthesis methods and calcination atmospheres, a series of MnOx/TiO2 catalysts were prepared. The contents and distributions of Mn2+, Mn3+ and Mn4+ in catalysts were tested through the titration method. The titration results showed that the content of Mn4+ was the highest during the precursor was Mn (NO3)2, while the content of Mn2+ in the catalysts calcinated in nitrogen atmosphere was the highest. The mechanisms of different MnOx states in the catalytic process were discussed. It was found that a mixture of more MnOx with low valence state and less MnOx with high valence state were beneficial to the catalytic process.