Li Ting-Yu, Wey Ming-Yen
Department of Environmental Engineering, National Chung Hsing University, Taichung, 402, Taiwan, ROC.
Department of Environmental Engineering, National Chung Hsing University, Taichung, 402, Taiwan, ROC.
J Environ Manage. 2025 Sep;391:126524. doi: 10.1016/j.jenvman.2025.126524. Epub 2025 Jul 9.
The detrimental effects of SO poisoning pose a critical challenge for the practical implementation of Mn-based catalysts in low-temperature NH-SCR systems for NO abatement. The causes of NH-SCR catalyst deactivation are the deposition of ammonium sulfates on the active sites and the formation of metal sulfates due to reactions between SO and the active metal oxide. Herein, a HO-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 HO/Mn molar ratio of 3 demonstrated a higher proportion of Mn, Ce, and O, and a larger pore size than MnCe-M (without HO). Crucially, MnCe-M-3H exhibits excellent low-temperature NH-SCR activity, achieving 85 % at 100 °C and 95 % at 150 °C, and the highest SO tolerance. Characterization of the spent catalysts revealed that increasing the catalyst pore size reduced sulfate deposition. Moreover, catalysts with enhanced oxidation abilities mitigate SO 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 proportions (8.3 %) and a low sulfate deposition rate (0.07 % h for ammonia sulfates, 0.20 % h for metal sulfates), demonstrating its highest SO 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 tolerance and practical applicability in low-temperature NH-SCR systems.
在用于低温NH-SCR系统中NO减排的锰基催化剂的实际应用中，SO中毒的有害影响构成了一项严峻挑战。NH-SCR催化剂失活的原因是活性位点上硫酸铵的沉积以及SO与活性金属氧化物之间反应形成金属硫酸盐。在此，采用了一种HO辅助的氧化还原沉淀法来定制锰铈基催化剂，通过扩大其孔径并增强其氧化能力，从而分别提高硫酸盐分解速率并减少金属硫酸盐的形成。结果，HO/Mn摩尔比为3的MnCe-M-3H比MnCe-M（无HO）表现出更高比例的Mn、Ce和O以及更大的孔径。至关重要的是，MnCe-M-3H表现出优异的低温NH-SCR活性，在100℃时达到85%，在150℃时达到95%，并且具有最高的SO耐受性。对失活催化剂的表征表明，增大催化剂孔径可减少硫酸盐沉积。此外，氧化能力增强的催化剂减轻了SO化学中毒，从而减少了金属硫酸盐的形成。具体而言具有最强氧化能力和大孔径的MnCe-M-3H-4S显示出最低的MnSO比例（8.3%）和低硫酸盐沉积速率（硫酸铵为0.07% h，金属硫酸盐为0.20% h），表明其具有最高的SO耐受性。本研究证实，增大锰铈基催化剂的孔径并增强其氧化能力可有效降低硫酸盐沉积速率和金属硫酸盐的形成，从而提高其在低温NH-SCR系统中的SO耐受性和实际适用性。
