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Modification of a three-way catalyst washcoat by aging: A study along the longitudinal axis

机译:通过老化对三效催化剂修补基面涂料的改性:沿纵轴的研究

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This work reports the research carried out by studying aliquots extracted at different axial coordinates from Three Way Catalyst (TWC) monoliths aged under real traffic conditions. Our study focused on the catalytic properties and on several chemical and physical effects caused in the Front and Rear monolith washcoat surfaces by vehicle aging after 60,000 km. Regarding the catalytic properties, all the used aliquots showed poorer activity than their corresponding fresh counterparts. The strongest deactivation was detected for NO and hydrocarbon conversion. CO conversion was less affected and the Rear monolith was as deactivated as the Front one. The characterisation techniques (TXRF, N-2, adsorption-desorption isotherms, XRD and H-2-TPR) detected - (i) the deposition of P, Zn and Pb; (ii) the formation Of CePO4 on account of the Ce from the washcoat; (iii) thermal sintering; (iv) inhibition of the reducibility of Ce oxides - as the main effects brought about by vehicle aging conditions. The deactivation observed at the beginning of the Front monolith was the result of a combination of the former effects. When moving downstream to higher axial coordinates, Pb accumulation and the loss of specific area appeared to be the only probable sources of deactivation. (c) 2005 Elsevier B.V. All rights reserved.
机译:这项工作报告了通过研究从三轴催化剂(TWC)整料在实际交通条件下老化的不同轴向坐标提取的等分试样而进行的研究。我们的研究集中在6万公里后车辆老化引起的前后整料修补基面表面的催化性能以及几种化学和物理效应。关于催化性能,所有使用的等分试样均比其相应的新鲜等分试样显示出较差的活性。检测到最强的失活是NO和烃转化。一氧化碳的转化受到的影响较小,后部的整体结构与前部的整体结构一样被停用。表征技术(TXRF,N-2,吸附-解吸等温线,XRD和H-2-TPR)检测-(i)P,Zn和Pb的沉积; (ii)由于修补基面涂层中的铈而形成CePO4; (iii)热烧结; (iv)抑制铈氧化物的还原性-这是车辆老化条件带来的主要影响。在前部整体结构开始时观察到的失活是前者效应共同作用的结果。当向下游移动到更高的轴向坐标时,铅的积累和比表面积的损失似乎是唯一可能的失活来源。 (c)2005 Elsevier B.V.保留所有权利。

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