Novel Mn–Ce–Ti Mixed-Oxide Catalyst for the Selective Catalytic Reduction of NO_<i>x</i> with NH₃

Mn–Ce–Ti mixed-oxide catalyst prepared by the hydrothermal method was investigated for the selective catalytic reduction (SCR) of NO_<i>x</i> with NH₃ in the presence of oxygen. It was found that the environmentally benign Mn–Ce–Ti catalyst exhibited excellent NH₃-SCR activity and strong resistance against H₂O and SO₂ with a broad operation temperature window, which is very competitive for the practical application in controlling the NO_<i>x</i> emission from diesel engines. On the basis of the catalyst characterization, the dual redox cycles (Mn⁴⁺ + Ce³⁺ ↔ Mn³⁺ + Ce⁴⁺, Mn⁴⁺ + Ti³⁺ ↔ Mn³⁺ + Ti⁴⁺) and the amorphous structure play key roles for the high catalytic deNO_<i>x</i> performance. Diffuse reflectance infrared Fourier transform spectroscopy studies showed that the synergetic effect between Mn and Ce contributes to the formation of reactive intermediate species, thus promoting the NH₃-SCR to proceed