Hydrothermal aging of Pt/Al2O3 monolith: Washcoat morphology degradation effects studied using ammonia and propylene oxidation
Hydrothermal aging of Pt/Al2O3 monolith: Washcoat morphology degradation effects studied using ammonia and propylene oxidation
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DOI：
10.1016/j.cattod.2017.12.023
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发表时间：
2019-01-15
期刊：
影响因子：
5.3
通讯作者：
Joshi, Saurabh
中科院分区：
文献类型：
--
作者：
Dhillon, Pritpal S.;Harold, Michael P.;Joshi, Saurabh
排放控制催化剂在恶劣的操作条件下会发生降解，对产品的分配和转化产生负面影响。理解和量化这种影响对于正确设计催化剂是必要的。本研究阐明了水热老化对用于氨和丙烯氧化的Pt/ γ Al2O3水洗涂层单体性能的影响，这两种反应体系分别与氨滑催化剂（ASC）和柴油氧化催化剂（DOC）有关。Pt/ γ - al2o3催化剂在550℃下含H2O的进料流中放置250小时以上。随着催化剂逐渐老化，以离散间隔测量催化剂的性能。结果表明，对于氨氧化，水热老化对Pt/Al2O3在250℃以下的活性影响可以忽略不计，但对超过300℃的活性影响显著，建立了一个（1D + 1D）反应器模型来预测观察到的活性随老化时间的下降。利用动力学和催化剂表征数据，反应器模型预测老化过程中涂层形态的变化可能是催化剂活性下降的潜在机制。实验结果与Pt/Al2O3催化剂氧化丙烯的模拟实验结果一致。
Emission control catalysts experience degradation under the severe operating conditions which can negatively impact the product distribution and conversion. Understanding and quantifying this impact is necessary to properly design the catalyst. This study elucidates the effect of hydrothermal aging on the performance of a Pt/gamma Al2O3 washcoated monolith used for oxidation of ammonia and of propylene, two reaction systems pertinent to the Ammonia Slip Catalyst (ASC) and Diesel Oxidation Catalyst (DOC), respectively. The Pt/gamma-Al2O3 catalyst was subjected to a feed stream containing H2O at 550 degrees C for over 250 h. The performance of the catalyst was measured at discrete intervals as it was progressively aged. The catalyst performance results reveal for ammonia oxidation that hydrothermal aging has a negligible impact on Pt/Al2O3 activity for temperatures below 250 degrees C but a significant detrimental impact for temperatures exceeding 300 degrees C. A (1D + 1D) reactor model was developed to predict the decline in the observed activity with aging time. Using kinetics and catalyst characterization data, the reactor model predicts that changes in washcoat morphology during aging is likely the underlying mechanism for the decline in activity of the catalyst. The results are corroborated with testing and modeling of propylene oxidation on the Pt/Al2O3 catalyst.