Buttignol Filippo, Garbujo Alberto, Biasi Pierdomenico, Kröcher Oliver, Ferri Davide
Paul Scherrer Institute, PSI Center for Energy and Environmental Sciences, CH-5232 Villigen, Switzerland.
Institute for Chemical Sciences and Engineering, École polytechnique fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.
J Am Chem Soc. 2025 Mar 12;147(10):8978-8990. doi: 10.1021/jacs.5c01100. Epub 2025 Feb 28.
Fe-exchanged zeolites are heterogeneous catalysts that can potentially ensure simultaneous conversion of nitrous oxide (NO) and nitric oxide (NO) using ammonia (NH) as a selective reducing agent through their selective catalytic reduction reaction (NO-NO-SCR). In this study, we rationalize the origin of the beneficial effect of NO on the NO conversion by combining catalytic experiments with characterization and in X-ray absorption spectroscopy (XAS) and infrared spectroscopy in diffuse reflectance mode (DRIFTS) on a series of Fe-ZSM-5 catalysts where we attempted to control Fe speciation at constant Fe content. The catalytic activity data revealed that NO can promote NO conversion at different temperatures and to different extents. This behavior was found to be related to the activity of the catalysts in the NO-mediated NO decomposition reaction, which ensures the oxidative transformation of NO and thus sustains the NO-NO-SCR chemistry. The oxidation activity is in turn determined by processes of NO activation and NO adsorption, which are a function of the Fe speciation and are likely catalyzed by a minority of isolated Fe sites coordinated in different cationic environments. In agreement, the concentrations of the Fe species able to activate NO () and of the Fe species able to coordinate NO () decrease with an increasing degree of Fe agglomeration and govern especially the promotion of the NO conversion induced by NO in this dual-site mechanism. Maximization of the concentration of both species is therefore essential to design Fe-exchanged zeolites with the highest activity toward the NO-NO-SCR reaction.
铁交换沸石是多相催化剂，通过选择性催化还原反应（NO-NO-SCR），以氨（NH）作为选择性还原剂，它们有可能确保同时转化一氧化二氮（N₂O）和一氧化氮（NO）。在本研究中，我们通过催化实验与表征相结合，利用X射线吸收光谱（XAS）和漫反射模式红外光谱（DRIFTS），对一系列试图在恒定铁含量下控制铁形态的Fe-ZSM-5催化剂进行研究，从而阐明了NO对NO转化产生有益影响的起源。催化活性数据表明，NO可以在不同温度下以不同程度促进NO转化。发现这种行为与催化剂在NO介导的NO分解反应中的活性有关，该反应确保了NO的氧化转化，从而维持了NO-NO-SCR化学过程。氧化活性又由NO活化和NO吸附过程决定，这些过程是铁形态的函数，并且可能由少数在不同阳离子环境中配位的孤立铁位点催化。一致的是，能够活化NO的铁物种（）和能够配位NO的铁物种（）的浓度随着铁团聚程度的增加而降低，并且在这种双位点机制中特别控制由NO引起的NO转化促进作用。因此，最大化这两种物种的浓度对于设计对NO-NO-SCR反应具有最高活性的铁交换沸石至关重要。
