Krishna Siddarth H, Jones Casey B, Miller Jeffrey T, Ribeiro Fabio H, Gounder Rajamani
Charles D. Davidson School of Chemical Engineering, Purdue University, 480 Stadium Mall Drive, West Lafayette, Indiana 47907, United States.
J Phys Chem Lett. 2020 Jul 2;11(13):5029-5036. doi: 10.1021/acs.jpclett.0c00903. Epub 2020 Jun 16.
NO selective catalytic reduction (SCR) with NH on Cu-zeolites is a commercial emissions control technology for diesel and lean-burn engines. Mitigating low-temperature emissions remains an outstanding challenge, motivating an improved understanding of the reaction mechanism, active site requirements, and rate-determining processes at low temperatures (<523 K). In this Perspective, we discuss how spectroscopy provides crucial information about how the structures, coordination environments, and oxidation states of Cu active sites depend on reaction conditions and sample composition; when combined with kinetic measurements, such data provide insights into the Cu site and spatial density requirements for reduction and oxidation steps relevant to the Cu(II)/Cu(I) SCR redox cycle. Isolated Cu ions coordinated to zeolite oxygen atoms become coordinated to NH and dynamically interconvert between mononuclear and binuclear NH-solvated Cu complexes to catalyze SCR turnovers. We conclude with future research directions that can benefit from combining quantitative kinetic measurements with spectroscopy.
在铜沸石上进行的以氨为还原剂的选择性催化还原（SCR）是一种用于柴油发动机和稀燃发动机的商业排放控制技术。减轻低温排放仍然是一个突出的挑战，这促使人们更好地理解低温（<523 K）下的反应机理、活性位点要求和速率决定过程。在这篇展望文章中，我们讨论了光谱学如何提供关于铜活性位点的结构、配位环境和氧化态如何依赖于反应条件和样品组成的关键信息；当与动力学测量相结合时，这些数据为与铜（II）/铜（I）SCR氧化还原循环相关的还原和氧化步骤的铜位点及空间密度要求提供了见解。与沸石氧原子配位的孤立铜离子与氨配位，并在单核和双核氨溶剂化铜配合物之间动态相互转化，以催化SCR反应。我们最后提出了未来的研究方向，这些方向可以从将定量动力学测量与光谱学相结合中受益。
