ABSTRACT
The effect of different MnOx loadings on NO conversion over MnOx-TiO2 catalysts prepared by the impregnation method was investigated. The NO conversion increased firstly and then tended to be stable with the increase of MnOx loading. When the MnOx loading reached 20 wt%, the conversion of NO reached 89.0% at 140°C. However, the N2 selectivity showed a downward trend as the increase of MnOx loading (0–30 wt%). This indicated that MnOx increased the NO conversion over the catalyst as well as widened the temperature window toward activity, but decreased the N2 selectivity. Afterward, the catalysts were characterized by BET, XRD, NO-TPD, NH3-TPD, and H2-TPR methods. The results showed that the addition of MnOx blocked the porous structure, further decreasing the specific surface area and pore volume of catalysts. However, a small amount of MnOx loading could be uniformly dispersed on the surface of the catalyst as a single layer, facilitating to enhancing the NO adsorption performance, NH3 adsorption performance, and redox performance of the catalysts, thereby increasing the catalysts' NO conversion efficiency, the catalytic reaction path of which conformed to the Langmuir-Hinshelwood mechanism. When the content of MnOx exceeded 20%, the MnOx would exist on the surface of the carrier in a crystalline form, and the NO conversion was difficult to continue to improve.
