Effect of propene, propane, and methane on conversion and oxidation state of three-way catalysts: a microwave cavity perturbation study
Effect of propene, propane, and methane on conversion and oxidation state of three-way catalysts: a microwave cavity perturbation study
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DOI：
10.1016/j.apcatb.2014.09.068
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发表时间：
2015-04-01
影响因子：
22.1
通讯作者：
Moos, Ralf
中科院分区：
文献类型：
--
作者：
Beulertz, Gregor;Votsmeier, Martin;Moos, Ralf
本文介绍了实验室反应器测量的稳态转化的污染物CO，碳氢化合物和NO的三效催化剂含有氧化铈作为储氧组分。它示出的饱和烃C3 H8或CH 4的存在下，导致的化学计量的最佳转换（CO-NO交叉）富燃料的组合物的转变。在较低的温度下，该转变更明显，并且可以通过烃氧化反应的动力学限制来解释。采用微波谐振腔微扰技术原位测量氧化铈的氧化态。在第一步中，进行滴定实验。通过用H-2/H2O混合物平衡将储氧水平调节至预定水平。实验表明，对于给定的温度，微波衍生的信号（这里是共振频率）与氧化铈的氧化态有很好的相关性。微波腔微扰技术，然后同时应用于稳态性能测试中存在的不同的烃。已发现，如果排气化学计量从稀燃斜升到富燃，则在所有情况下的CO-NO交叉点与氧化铈的氧化态的强烈降低一致。催化剂的氧化态和催化性能之间的相关性被发现是独立的催化剂温度和烃的性质。利用微波谐振腔微扰技术可以精确地确定CO-NO交叉点。结果表明，在某些情况下，基于微波的测量可以允许比通过λ传感器的常规控制更精确地控制催化剂性能。(C)2014爱思唯尔有限公司版权所有。
This paper presents laboratory reactor measurements of the steady-state conversion of the pollutants CO, hydrocarbons and NO over a three-way catalyst containing ceria as an oxygen-storage component. It is shown that the presence of the saturated hydrocarbons C3H8 or CH4 causes a shift in the stoichiometry of optimal conversion (CO-NO crossover) to fuel-rich compositions. The shift was more pronounced at lower temperatures and can be explained by the kinetic limitation of the hydrocarbon oxidation reaction. A microwave cavity perturbation technique was used to measure in situ the oxidation state of the ceria. In a first step, titration experiments were performed. The oxygen-storage level was adjusted to a predefined level by equilibration with a H-2/H2O mixture. The experiments showed that for a given temperature, the microwave-derived signal (here the resonance frequency) correlates well with the oxidation state of ceria. The microwave cavity perturbation technique was then applied simultaneously to steady-state performance tests in the presence of different hydrocarbons. It was found that if the exhaust stoichiometry is ramped from lean to fuel rich, the CO-NO crossover point in all cases coincides with a strong decrease in the oxidation state of ceria. The correlation between the oxidation state of the catalyst and the catalytic performance is found to be independent of the catalyst temperature and the nature of the hydrocarbon. The CO-NO crossover point can be precisely determined by the microwave cavity perturbation technique. The results suggest that a microwave-based measurement may, under some circumstances, allow for a more precise control of the catalyst performance than the conventional control by lambda sensors. (C) 2014 Elsevier B.V. All rights reserved.