Adjustment of operation temperature window of Mn-Ce oxide catalyst for the selective catalytic reduction of NOx with NH3.

In order to enhance the catalytic activity of Mn-Ce oxide catalyst for the selective catalytic reduction of NOx with NH3 (NH3-SCR), W was introduced as a promoter. With the doping of W, the NOx conversion over Mn3CeOx catalyst above 150 °C was increased, and the N2O production was significantly decreased. Even in the present of water vapour, Mn3CeW0.3Ox still showed a good SCR activity. H2-TPR and XPS results suggested that the doping of tungsten could inhibit the charge imbalance and reducibility, which would inhibit NO oxidation to NO2 over Mn3CeOx. As a result, the NOx conversion below 150 °C over Mn3CeW0.3Ox was slightly lower than that over Mn3CeOx. Since the NOx production and the NH3 conversion during the NH3 oxidation of Mn3CeOx were inhibited after the doping of W, the NOx conversion above 150 °C over Mn3CeW0.3Ox was higher than that over Mn3CeOx. The transient reaction demonstrated that the doped W species on Mn3CeW0.3Ox could inhibit the N2O produced by the Langmuir-Hinshelwood mechanism. Kinetic study proved that νSCR over Mn3CeW0.3Ox was obviously higher that over Mn3CeOx, νNSCR and νC-O over Mn3CeOx were much higher than those of Mn3CeW0.3Ox, which were consistent with the SCR activity.