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The sintering of supported palladium automotive catalysts.

机译：负载型钯汽车催化剂的烧结。

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This dissertation was directed to studying catalyst sintering, which is an important form of catalyst deactivation. A better understanding of this phenomenon will be of great help in the applications of catalyst under high temperature, such as automotive emission control and catalytic combustion.; This work focuses on Pd based catalysts since they are the most likely candidates for close-coupled catalytic converters. While concentrating on Pd, Pt and Au catalysts were also studied in order to compare their sintering behaviors with that of Pd catalysts. A novel approach to prepare gold catalyst based on aqueous impregnation from a gold chloride precursor has been developed to prepare highly dispersed catalysts. These catalysts have low chloride content and excellent hydrothermal stability. The activity of these catalysts compares favorably with the most active catalysts prepared reported in the literature prepared by the deposition precipitation method.; Multiple techniques have been applied to measure the metal particle size in Pd/SCCa catalysts. Good agreement was obtained between various techniques, meaning that the analytical methods employed in our research (TEM, XRD, chemisorption and CO oxidation) are internally consistent and provide a reliable measure of the change in metal particle size and dispersion as a function of sintering time.; The kinetic study of Pd catalysts suggests that its sintering under study conditions proceeds by Ostwald ripening.; It is shown in this work that both sintering mechanisms can lead to log normal particle size distribution (PSD). In other words, PSD alone cannot be used alone to differentiate sintering mechanisms.; Various factors influencing support sintering were investigated. It was found that The BET surface area of support only has a limited effect on catalyst sintering. So does the metal loading of catalyst.; It was found that melting point, heat of sublimation or Tamman temperature are not the reliable indicators for sintering behavior, while the model of atomic weight is a promising one.
机译：本文旨在研究催化剂的烧结，这是催化剂失活的一种重要形式。更好地理解这一现象将对高温催化剂的应用，如汽车排放控制和催化燃烧，有很大帮助。这项工作集中在基于Pd的催化剂上，因为它们最有可能成为紧密耦合催化转化器的候选材料。在集中于Pd的同时，还研究了Pt和Au催化剂，以比较它们与Pd催化剂的烧结行为。已经开发了一种基于从氯化金前体的水性浸渍制备金催化剂的新颖方法，以制备高度分散的催化剂。这些催化剂具有较低的氯化物含量和优异的水热稳定性。这些催化剂的活性与通过沉积沉淀法制备的文献中报道的最具活性的催化剂相比具有优势。已经应用了多种技术来测量Pd / SCCa催化剂中的金属粒度。各种技术之间取得了良好的一致性，这意味着我们研究中使用的分析方法（TEM，XRD，化学吸附和CO氧化）在内部是一致的，并提供了可靠的方法来衡量金属粒径和分散度随烧结时间的变化。;钯催化剂的动力学研究表明，在研究条件下进行的烧结是通过奥斯特瓦尔德熟化进行的。这项工作表明，两种烧结机制都可以导致对数正态粒度分布（PSD）。换句话说，不能单独使用PSD来区分烧结机制。研究了影响支撑烧结的各种因素。发现载体的BET表面积仅对催化剂烧结具有有限的影响。催化剂的金属负载也是如此。发现熔点，升华热或塔曼温度不是烧结行为的可靠指标，而原子量模型是一个有前途的模型。

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