Mesoporous MnOx-CeO₂ composites for NH₃-SCR: the effect of preparation methods and a third dopant

In this study, different preparation methods including an oxalate route, a nano-casting strategy and a traditional co-precipitation route were applied to obtain MnOx-CeO₂ mixed oxides for selective catalytic reduction (SCR) of NO with NH₃. The catalyst prepared from the oxalate route showed improved performance for NOx conversion and SO₂ + H₂O durability. To further improve the SO₂ and H₂O resistance of catalysts, ternary oxides were prepared from the oxalate route. The catalysts were studied by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area analysis, X-ray photoelectron spectroscopy (XPS), H₂ temperature-programmed reduction (H₂-TPR), NH₃ temperature-programmed desorption (NH₃-TPD), SO₂ temperature-programmed desorption (SO₂-TPD), and in situ diffuse reflectance infrared fourier transform spectroscopy (in situ DRIFTS). The nickel-manganese-cerium ternary oxide showed the best SO₂ and H₂O durability. The reason can be ascribed to its smaller pores, amorphous structure, and moderate amount of surface Mn³⁺/oxygen species, which could decrease chemical adsorption of SO₂.