NH3-TPD methodology for quantifying hydrothermal aging of Cu/SSZ-13 SCR catalysts
NH3-TPD methodology for quantifying hydrothermal aging of Cu/SSZ-13 SCR catalysts
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DOI：
10.1016/j.ces.2018.06.015
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发表时间：
2018-11-23
影响因子：
4.7
通讯作者：
Yezerets, Aleksey
中科院分区：
文献类型：
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作者：
Luo, Jinyong;Kamasamudram, Krishna;Yezerets, Aleksey
我们在Cu/SSZ-13催化剂中发现了一个新的酸性特征，这与NH3-TPD图谱中存在两个不同的脱附峰有关，以及它们在温和水热老化后相对强度的变化(Luo等人，2017)。在这项工作中，我们将这些发现转化为一种敏感的实验室诊断方法，用于基于两个NH3-TPD峰值的比率来量化累积老化暴露。我们还讨论了将这种方法应用于真实世界老化样品的一些实际方面，通过分离硫中毒和催化剂负载可变性的影响。该方法得到了一个简单的铜/SSZ-13催化剂水热老化动力学模型，并对老化过程的实际相关方面提供了一些有用的见解。特别是，我们已经证明了老化是累积的，曝光步骤的顺序并不重要。所建立的模型的另一个重要结果是与老化过程的陡峭的温度依赖性有关(E-a约为168kJ/mol)。因此，发动机上的大部分操作暴露，通常低于400摄氏度，对催化剂老化没有明显影响。相反，这种老化几乎完全是由周期性的高温事件引起的，例如与各种系统再生机制有关的事件。我们通过400℃下1000小时的老化试验验证了这一观察结果。最后，我们预计所开发的诊断和量化累积水热老化的方法也适用于其他类型的催化剂，包括氨氧化催化剂(AMOX)和SCR on Filter(SCRF)，因为它是基于这种金属交换沸石的固有性质。(C)2018爱思唯尔有限公司。保留所有权利。
We identified a new acidic feature in Cu/SSZ-13 catalysts, related to the presence of two distinct desorption peaks in the NH3-TPD profiles, and to the changes in their relative intensity in response to mild hydrothermal aging (Luo et al., 2017). In this work, we have translated those findings into a sensitive laboratory diagnostic methodology for quantifying cumulative aging exposure, based on the ratio of the two NH3-TPD peaks. We have also addressed some practical aspects of applying this methodology to real-world aged samples, by decoupling the effects of sulfur poisoning and of the catalyst loading variability. The developed method yielded a simple kinetic model of the Cu/SSZ-13 catalysts hydrothermal aging, and some useful insights into the practically relevant aspects of the aging process. In particular, we have shown that the aging is cumulative, and that the sequence of the exposure steps does not matter. One other important consequence of the developed model is related to the steep temperature dependence of the aging process (E-a approximate to 168 kJ/mol). As a result, the majority of the on-engine operation exposure, typically below similar to 400 degrees C, has no appreciable impact on the catalyst aging. In contrast, such aging is almost entirely induced by the periodic high-temperature events, such as those related to various system regeneration regimes. We have verified that observation by a 1000-h aging test at 400 degrees C.Finally, we expect that the developed method of diagnosing and quantifying cumulative hydrothermal age can be applicable to other types of catalysts which include Cu/SSZ-13 in their formulation, including ammonia oxidation catalysts (AMOX) and SCR on filter (SCRF), since it is based on the intrinsic properties of this metal-exchanged zeolite. (C) 2018 Elsevier Ltd. All rights reserved.