Characteristics of Pt-K/MgAl₂O₄ lean NOx trap catalysts

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• 作者：Do Heui Kim^a ; ^b ; ^{dohkim@snu.ac.kr} ; K. Mudiyanselage^a ; J. Szá ; nyi^a ; H. Zhu^a ; J.H. Kwak^a ; Charles H.F. Peden^a
• 关键词：Pt&ndash ; K/MgAl2O4 ; Lean NOx trap catalyst ; MgAl2O4 support ; FTIR ; K loading ; Durability
• 刊名：Catalysis Today
• 出版年：2012
• 期刊代码：13_09205861
• 类别：ce
• 出版时间：30 April, 2012
• 卷：184
• 期：1
• 页码：2-7
• 文件大小：592 K

摘要

We report the various characteristics of Pt-K/MgAl₂O₄ lean NOx trap (LNT) catalysts including the effect of K loading on nitrate formation/decomposition, NOx storage activity, and durability. This work provides results aimed at developing a fundamental understanding of this new class of LNT catalysts, which could be good candidates for high temperature engine exhaust NOx removal applications. Upon the adsorption of NO₂ on K/MgAl₂O₄ samples, potassium nitrates, formed at Mg-related sites on the MgAl₂O₄ support material surface, are observed in addition to the two (ionic and bidentate) potassium nitrate species observed to form on Al₂O₃-supported samples. Based on NO₂ TPD and FTIR results, the Mg-bound KNO₃ species thermally decompose at higher temperatures than Al-bound KNO₃, implying its superior thermal stability. At a potassium loading of 5 wt%on MgAl₂O₄, the temperature of maximum NOx uptake (T_max) is 300 掳C. Increasing the potassium loading from 5 wt%to 10 wt%results in a monotonic shift in the T_max to 450 掳C, demonstrating an unexpectedly significant dependence of T_max on the potassium loading. Further increases in potassium loading above 10 wt%, however, only give rise to a reduction in the overall NOx storage capacity. This work also highlights the obstacles to the implementation of these materials for practical applications associated with their durability and sulfur poisoning/removal.