Facile control of surface properties in CeO2-promoted Mn/TiO2 catalyst for low-temperature selective catalytic reduction of NO by NH3

Abstract

Although the metal loading sequence can highly influence the bimetallic catalyst performance, they are generally applied to the reaction experiments without investigating the metal impregnation sequence. In this study, therefore, we investigated the surface properties of CeO2-promoted Mn/TiO2 catalysts with different impregnation sequences of Mn and Ce in the low-temperature selective catalytic reduction (SCR) of NO by NH3. We observed that the catalyst performance depended on simply changing the impregnation method of Mn and Ce in the catalyst activity test for the low-temperature SCR reaction. The co-impregnated catalyst, Mn-Ce/TiO2, achieved much higher NO conversion than other catalysts. Additionally, X-ray diffraction, transmission electron microscopy, N2 adsorption/desorption experiments, H2 temperature-programmed reduction (H2-TPR), NO/NH3 temperature-programmed desorption (NO/NH3-TPD), X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared spectroscopy (FTIR) were performed to identify the influence of this simple change on the catalyst. These characterization results indicated that metal dispersion improved in the co-impregnated catalyst compared to the sequentially impregnated catalysts, and these well-distributed metal particles (Mn-Ce/TiO2 catalyst) could produce defect formation on the catalyst, thereby serving more NOx/NH3 adsorption sites. Moreover, it was found that catalyst acidity could be simply controlled by changing synthesis method although it contained same metal composition. This knowledge will be useful for the design of catalyst for low temperature NH3-SCR of NO.