Novel Mn-Ce-Ti mixed-oxide catalyst for the selective catalytic reduction of NOx with NH₃.

Mn-Ce-Ti mixed-oxide catalyst prepared by the hydrothermal method was investigated for the selective catalytic reduction (SCR) of NOx 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 NOx emission from diesel engines. On the basis of the catalyst characterization, the dual redox cycles (Mn(4+) + Ce(3+) ↔ Mn(3+) + Ce(4+), Mn(4+) + Ti(3+) ↔ Mn(3+) + Ti(4+)) and the amorphous structure play key roles for the high catalytic deNOx 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.