Spectroscopic and kinetic responses of Cu-SSZ-13 to SO2 exposure and implications for NOx selective catalytic reduction-猫眼课题宝

DOI：

10.1016/j.apcata.2019.01.024

发表时间：

2019-03

期刊：

Applied Catalysis A: General

影响因子：

通讯作者：

中科院分区：

其他

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作者：

Arthur J. Shiha;Ishant Khuranaa;Hui Lib;Juan Gonzáleza;Ashok Kumard;Christopher Paoluccib;Trevor M. Lardinoisa;Casey B. Jonesa;Jonatan D. Albarracin Caballeroa;Krishna Kamasamudramd;Aleksey Yezeretsd;W. N. Delgassa;Jeffrey T. Millera;Aída Luz Villac;William F. Schneiderb;Rajamani Goundera;Fabio H. Ribeiroa

通过在473和673 K下将铜-沸石粉体样品暴露于干燥的SO2和O2流中，然后使用光谱和动力学评估分析表面中间产物，研究了硫中毒对用于氨选择性催化还原（SCR）氮氧化物（NOX）的Cu-SSZ-13沸石的影响。模型Cu-SSZ-13沸石合成含有不同的Cu活性中心类型，主要是二价Cu 2+离子在近骨架Al（Z2 Cu）上交换，或单价CuOH+络合物在孤立骨架Al（ZCuOH）上交换。SCR周转率（473 K，每铜）线性下降，增加S含量检测不到的值在等摩尔S：铜的比例，与中毒的每个铜网站与一个SO2衍生的中间体。Cu和S K边X射线吸收光谱和密度泛函理论计算用于确定Z2 Cu和ZCuOH位点处不同SO2衍生中间体的结构和结合能，揭示了硫酸氢盐的能量特别低，并且残余的Brønsted质子在Z2 Cu位点处被释放，形成硫酸氢盐。分子动力学模拟还表明，与一个HSO 4 −结合的Cu位是不移动的，但与两个HSO 4 −结合时，Cu位从骨架中释放出来，并且具有更高的移动的。这些结果表明，Z2 Cu位比ZCuOH位更耐SO2中毒，并且一旦中毒更容易再生。

The effects of sulfur poisoning on Cu-SSZ-13 zeolites, used commercially for the selective catalytic reduction (SCR) of nitrogen oxides (NOX) with ammonia, were studied by exposing model Cu-zeolite powder samples to dry SO2and O2streams at 473 and 673 K, and then analyzing the surface intermediates formed using spectroscopic and kinetic assessments. Model Cu-SSZ-13 zeolites were synthesized to contain distinct Cu active site types, predominantly either divalent Cu2+ions exchanged at proximal framework Al (Z2Cu), or monovalent CuOH+complexes exchanged at isolated framework Al (ZCuOH). SCR turnover rates (473 K, per Cu) decreased linearly with increasing S content to undetectable values at equimolar S:Cu ratios, consistent with poisoning of each Cu site with one SO2-derived intermediate. Cu and S K-edge X-ray absorption spectroscopy and density functional theory calculations were used to identify the structures and binding energies of different SO2-derived intermediates at Z2Cu and ZCuOH sites, revealing that bisulfates are particularly low in energy, and residual Brønsted protons are liberated at Z2Cu sites as bisulfates are formed. Molecular dynamics simulations also show that Cu sites bound to one HSO4−are immobile, but become liberated from the framework and more mobile when bound to two HSO4−. These findings indicate that Z2Cu sites are more resistant to SO2poisoning than ZCuOH sites, and are easier to regenerate once poisoned.

Spectroscopic and kinetic responses of Cu-SSZ-13 to SO2 exposure and implications for NOx selective catalytic reduction

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