Manganese oxides supported on multi-walled carbon nanotubes for selective catalytic reduction of NO with NH3: Catalytic activity and characterization

A series of catalysts of manganese oxides supported on multi-walled carbon nanotubes (MWCNTs) modified by oxygen dielectric barrier discharge plasma were prepared by the pore volume impregnation method, and the catalysts were characterized by TEM, XRD, XPS, N2 adsorption, H2-TPR, and Raman spectroscopy methods. The effects of Mn loading, calcination temperature, and MWCNTs outer diameter on selective catalytic reduction (SCR) of NO with NH3 were investigated, and the SCR activity tests were carried out in a fixed-bed reactor. The results showed that MnOx dispersion on MWCNTs varied with the Mn loading, calcination temperature, and MWCNTs outer diameter. Three states of manganese species (MnO2, Mn3O4, and MnO) coexisted in MnOx/MWCNTs catalysts, and most of the Mn existed as MnO2 and Mn3O4. Additionally, among the MnOx/MWCNTs catalysts prepared, MWCNTs (60–100 nm) supported 10 wt.% manganese calcined at 400 °C catalyst presented the best SCR activity under the conditions of 1000 ppm NH3, 1000 ppm NO and 5 vol.% O2. Well dispersed MnOx on MWCNTs, high concentration of MnO2 and low concentration of MnO would lead to high SCR activity.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► The states of Mn existed as Mn2O3 were not detected in MnOx/MWCNTs, which was rarely reported. ► MnO2 played important role in the SCR activity of MnOx/MWCNTs. ► The optimal preparation conditions of MnOx/MWCNTs catalyst were determined. ► High SCR activity was obtained in the MnOx/MWCNTs catalyst.