Unveiling the remarkable deNOx performance of MnMoVOx catalysts via dual regulation of the redox and acid sites
Unveiling the remarkable deNOx performance of MnMoVOx catalysts via dual regulation of the redox and acid sites
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DOI：
10.1016/j.apcatb.2023.123612
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发表时间：
2023-12
期刊：
影响因子：
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通讯作者：
Yonglong Li;Guobo Li;Yu Zou;Wenming Liu;Hongxiang Zhang;Shengyong Lu;Zhenguo Li;Shule Zhang-Shule-Zh
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文献类型：
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作者：
Yonglong Li;Guobo Li;Yu Zou;Wenming Liu;Hongxiang Zhang;Shengyong Lu;Zhenguo Li;Shule Zhang-Shule-Zh
开发具有优异的NO转化率、N2选择性和低温耐碱性的NH3-SCR催化剂仍然是一个巨大的挑战。基于MnOx的催化剂由于其优异的低温NH3-SCR活性而引起关注。然而，它们的强氧化能力往往会导致过量的NH3氧化，导致窄的操作温度窗口和低的N2选择性。在这项研究中，我们采用Mo和V，同时微调MnOx的酸性和氧化还原位点，有效地抑制了在中高温下的过量NH3氧化。调整后的Mn0.90Mo0.09V0.01Ox催化剂表现出优异的低温活性、显著更宽的活性温度窗口和对碱金属中毒的稳健抗性。多个表征结果表明，这种双酸-氧化还原位调控策略适当地削弱了氧化能力，同时显着提高了催化剂的表面酸性。此外，结合原位DRIFTS和DFT计算表明，随着Mo和V在MnOx上的调整，产生了新的Brønsted酸中心。此外，调控后的催化剂明显抑制了NO的吸附和硝酸盐物种的形成，从而完全通过E-R机理促进反应，提高了N2选择性。本研究还表明，最佳的NH3-SCR催化剂的性能时，实现氧化能力和酸性中心的和谐平衡，而不是遵循“越强越好”的趋势。此外，通过有效的双活性中心调节，K中毒催化剂保持了令人满意的催化活性。因此，本研究提出的双活性中心调控策略为高性能加氢催化剂的开发提供了有益的启示。
Developing NH3-SCR catalysts possessing excellent NO conversion, N2selectivity, and alkali-tolerance at low-temperatures remains a great challenge. MnOx-based catalysts have attracted attention due to their exceptional low-temperature NH3-SCR activity. However, their strong oxidative capabilities often lead to excessive NH3oxidation, causing a narrow operating temperature window and low N2selectivity. In this study, we employed Mo and V to simultaneously fine-tune the acid and redox sites of MnOx, effectively suppressing the excessive NH3oxidation at medium-high temperatures. The adjusted Mn0.90Mo0.09V0.01Oxcatalyst demonstrated excellent low-temperature activity, a significantly broader active temperature window, and robust resistance to alkali metal poisoning. Multiple characterization results indicate that this dual acid-redox sites regulation strategy appropriately weakens the oxidative capacity while notably enhances surface acidity of the catalyst. Furthermore, the combination of in situ DRIFTS and DFT calculations reveal that following the adjustments of Mo and V on MnOx, new Brønsted acid sites are generated. Besides, the regulated catalyst evidently inhibits NO adsorption and nitrate species formation, thus promoting the reaction exclusively through the E-R mechanism, resulting in boosted N2selectivity. This study also demonstrates that the optimum NH3-SCR performance of catalyst is achieved when oxidation ability and acid sites are harmoniously balanced, rather than following a "stronger is better" trend. In addition, through effective dual-active site regulation, the K-poisoning catalyst retains satisfactory catalytic activity. Thereby, the proposed dual-active sites regulation strategy in this study offers beneficial insights for the development of high-performance denitration catalysts.