Enabling Wide-Temperature Selective Catalytic Reduction of NOX via Modulating Redox Ability of Mn-Based Catalysts

Nitrogen oxides (NOX) emitted from marine diesel engines have appealed for efficient catalysts with a wide operation window for selective catalytic reduction of NOX by NH3 (NH3-SCR). However, challenges in the balance between the redox sites and proper acidic sites on the surface of catalysts restricted the development of wide-temperature range NH3-SCR catalysts. Herein, we reported a facile method to manipulate the redox ability of MnOx to improve the low-temperature SCR activity. The modified MnOx catalysts (MnOx-350-air + NH3) exhibited above 80% NO conversion and 100% selectivity to N2 in a wide temperature range from 150 to 500 °C (NO = NH3 = 1000 ppm, O2 = 7%, GHSV = 7200 h–1) and showed higher water resistance ability than the counterpart MnOx precursor catalyst. XPS and H2-TPR results revealed that the redox capability was improved significantly by changing the ratio of Mn4+/Mnn and Oα/(Oα+Oβ), resulting in the promotion of the adsorption and oxidation of NO to facilitate "fast SCR". NH3-TPD results revealed that the preparation method could controllably adjust the redox ability of catalysts without affecting the amount of B acid sites on their surface. This work might provide insight into the deliberate design of catalysts with a wide operating window for controlling NOx.