Suggested mechanisms for NH₃−SCR on V₂O₅/TiO₂ based catalysts contain both oxidized and reduced vanadium species. The degree of reduction and the importance of the redox properties of the catalyst are however still widely discussed. Here we show the presence of significant amounts of oxidovanadium(IV), VO²⁺ using electron paramagnetic resonance (EPR) spectroscopy of V₂O₅/TiO₂ and V₂O₅/WO₃/TiO₂ under operando selective catalytic reduction (SCR) of NO with NH₃ in a fixed bed plug flow reactor operating at high space velocity: 420,000 h⁻¹. The V(IV) content at the completely oxidized and reduced states is also analyzed. It is found that a significant part of the vanadium is reduced to the EPR active species, VO²⁺ at operando SCR conditions and even more when O₂ is removed from the SCR gas.

中文翻译：

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使用Operando EPR光谱仪评估NH3-SCR期间V（IV）的重要性

在V ₂ O ₅ / TiO ₂基催化剂上建议的NH ₃ -SCR机理既包含氧化钒也包括还原钒。然而，催化剂的还原程度和氧化还原性能的重要性仍被广泛讨论。在这里，我们通过操作选择性催化还原下V ₂ O ₅ / TiO ₂和V ₂ O ₅ / WO ₃ / TiO _2的电子顺磁共振（EPR）光谱显示了大量的氧化钒（IV），VO ²⁺的存在（ SCR）的NO与NH ₃在以高空速运行的固定床活塞流反应器中：420,000 h ^-1。还分析了在完全氧化和还原状态下的V（IV）含量。发现在操作SCR条件下，钒的大部分被还原为EPR活性物质，VO ²⁺，而从SCR气体中除去O ₂时，钒的还原率甚至更高。