Advancements in SO2 tolerance for low-temperature NH3-SCR through tailoring oxidation ability and pore size in MnCe-based catalysts
Ting-Yu Li, Ming‐Yen Wey
Abstract
The detrimental effects of SO 2 poisoning pose a critical challenge for the practical implementation of Mn-based catalysts in low-temperature NH 3 -SCR systems for NO X abatement. The causes of NH 3 -SCR catalyst deactivation are the deposition of ammonium sulfates on the active sites and the formation of metal sulfates due to reactions between SO 2 and the active metal oxide. Herein, a H 2 O 2 -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 H 2 O 2 /Mn molar ratio of 3 demonstrated a higher proportion of Mn 4+ , Ce 3+ , and O Lat , and a larger pore size than MnCe-M (without H 2 O 2 ). Crucially, MnCe-M-3H exhibits excellent low-temperature NH 3 -SCR activity, achieving 85 % at 100 °C and 95 % at 150 °C, and the highest SO 2 tolerance. Characterization of the spent catalysts revealed that increasing the catalyst pore size reduced sulfate deposition. Moreover, catalysts with enhanced oxidation abilities mitigate SO 2 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 MnSO 4 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 SO 2 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 SO 2 tolerance and practical applicability in low-temperature NH 3 -SCR systems.