Advancements in SO2 tolerance for low-temperature NH3-SCR through tailoring oxidation ability and pore size in MnCe-based catalysts.

The detrimental effects of SO2 poisoning pose a critical challenge for the practical implementation of Mn-based catalysts in low-temperature NH3-SCR systems for NOX abatement. The causes of NH3-SCR catalyst deactivation are the deposition of ammonium sulfates on the active sites and the formation of metal sulfates due to reactions between SO2 and the active metal oxide. Herein, a H2O2-assisted redox precipitation method has been employed to tailor MnCe-based catalysts by enlarging their pore size and enhancing their oxidation ability, thereby respectively increasing sulfate decomposition rates and reducing metal sulfate formation. As a result, MnCe-M-3H with an optimal H2O2/Mn molar ratio of 3 demonstrated a higher proportion of Mn4+, Ce3+, and OLat, and a larger pore size than MnCe-M (without H2O2). Crucially, MnCe-M-3H exhibits excellent low-temperature NH3-SCR activity, achieving 85 % at 100 °C and 95 % at 150 °C, and the highest SO2 tolerance. Characterization of the spent catalysts revealed that increasing the catalyst pore size reduced sulfate deposition. Moreover, catalysts with enhanced oxidation abilities mitigate SO2 chemical poisoning, thereby reducing the formation of metal sulfates. Specifically, MnCe-M-3H-4S, with the strongest oxidation ability and large pore size, showed the lowest MnSO4 proportions (8.3 %) and a low sulfate deposition rate (0.07 % h-1 for ammonia sulfates, 0.20 % h-1 for metal sulfates), demonstrating its highest SO2 tolerance. This study confirms that increasing the pore size and enhancing the oxidation ability of MnCe-based catalysts effectively reduce both the sulfate deposition rate and metal sulfate formation, thereby improving their SO2 tolerance and practical applicability in low-temperature NH3-SCR systems.