The Role of Medium Acid Sites Tuned by Ce Adding in Moderate-Temperature NH3-SCR

To develop highly efficient NH3-SCR catalysts with a wide temperature range, catalysts based on MnAlOx and Cerium elements loading with various mixing ratios were prepared for selective catalytic reduction of NO by NH3. The special role of cerium was demonstrated by the surface structure characteristics and unique catalytic performance, involving the surface-active sites and compositions analysis. Interestingly, the strengthening of Mn1.2Al0.8CeaOx on both acid sites, especially medium acids and strong acids, were clearly manifested. Meanwhile, the strong interaction between MnAlOx and CeO2 enabled favorable electron transfers from MnOx to CeO2 while generating more oxygen vacancies and active oxygen species, consequently accelerating the redox cycle. The results illustrate that the NOx conversion and the selectivity of N-2 can be improved with more medium acids tuned by appropriate Ce adding. However, an opposite effect will appear by excessive addition. In addition, the reaction mechanisms at different acid sites are revealed. Our findings, therefore, provide a strategy for the rational design of moderate-temperature NH3-SCR catalysts through adding-induced component engineering of composite materials.

Automated summary

The addition of cerium enhances the effect of MnAlOx on acidic sites, which improves the conversion of NOx and the selectivity of N-2. However, an opposite effect is observed with excessive addition. Rational design of composite materials through component engineering can optimize the performance of moderate-temperature NH3-SCR catalysts.