Study on NH3-SCR performance and mechanism of Mn supported SO42−-CeCO3F-CePO4 catalysts

Abstract

In this paper, NH3-SCR catalysts were prepared by impregnating transition metal Mn loaded on SO42−-CeCO3F-CePO4 and adding sulphuric acid to further improve the denitrification performance of the catalysts. The optimum performance of the catalysts was explored by varying the loading ratio of Mn and the concentration of sulphuric acid. XRD, Raman, NH3-TPD, H2-TPR, XPS and In situ DRIFTS were used to characterise the changes in the surface properties of the catalyst after loading with Mn and to investigate the reaction mechanism. The results show that the denitrification performance of the catalyst was improved after the loading of Mn and sulphuric acid treatment, and the temperature window became wider, with the denitrification rate consistently remaining above 80% at 200∼400 °C and the denitrification activity reaching 92.6% at 250 °C. Suitable Mn and sulphuric acid content allow for greater Mn-Ce interactions, resulting in better dispersion of active substances such as Mn oxides, MnSO4 and MnSO3, which can provide more adsorption and active sites and increase the reaction rate. The Mn atoms replace some of the Ce atoms in the CeO2 lattice, increasing the mobility of oxygen and thus improving the low-temperature activity of the catalyst. In situ IR results show that the catalyst follows both the Eley-Rideal mechanism and the Langmuir-Hinshelwood mechanism at 250 °C. The acidic sites on the surface are abundant and the Lewis acidic sites are the main active sites on the catalyst surface. Both mechanisms work together to facilitate the denitrification reaction.