Mechanism of NOx storage in ceria containing storage reduction catalyst materials

尽管第一代氮氧化物储存还原催化剂（Pt/BaO/Al2O3）取得了成功，但迫切需要进一步发展氮氧化物储存还原催化剂技术，以提高效率和耐久性，并满足未来的氮氧化物排放标准。其中包括开发更有效的存储和支持材料，以对抗热降解和硫中毒导致的长期稳定性降低。如文献所述，在NOx存储还原催化剂（Pt/BaO/CeO2/Al2O3）中存在铈，可以在高达300°C的温度下增加NOx存储容量，并提高稳定性。然而，对于这种含氧化铈的NOx储存还原催化剂的操作方式仍缺乏基本的了解。因此，该项目的目标是阐明在高达300°C的温度下，使用氧化钡/氧化铈混合系统，氧化铈对NOx储存机制和储存组件性能的影响。首先研究氧化钡/氧化铈混合体系，然后研究支撑（Al2O3）和诺贝尔金属（Pt）成分。为了阐明不同含铈材料的NOx储存机制，将采用在第一个创始时期开发的原位拉曼/FTIR方法。这种方法结合了原位拉曼光谱与定量FTIR气相分析在原位拉曼电池出口的潜力。这些研究包括确定相应的氮氧化物储存容量。由于含NOx储存还原催化剂的复杂性，将通过x射线光电子能谱（XPS）与拉曼和紫外-可见光谱相结合的详细研究来支持原位拉曼表征。由于NOx储存还原催化剂的稳定性与其对硫中毒的敏感性密切相关，因此研究硫（如SO2）对其的影响是本项目的重点之一。此外，还将研究废气中体积分数较大的其他组分（CO2, H2O）的影响。它们的存在可能会显著影响氮氧化物的储存机制，正如在第一个资助期对H2O所证明的那样。

Despite the success of the first generation of NOx storage reduction catalysts (Pt/BaO/Al2O3) further developments of NOx storage reduction catalyst technology are urgently needed to improve the efficiency and durability as well as to meet future NOx emission standards. These include the development of more efficient storage and support materials countering a reduction in long term stability by thermal degradation and sulfur poisoning. As described in the literature, the presence of ceria in NOx storage reduction catalysts (Pt/BaO/CeO2/Al2O3) leads to an increase in NOx storage capacity at temperatures up to 300°C as well as to improved stability. However, a fundamental understanding of the mode of operation of such ceria containing NOx storage reduction catalysts is still missing. Thus the goal of this project is to elucidate the influence of ceria on the NOx storage mechanism and the properties of the storage component at temperatures up to 300°C using barium oxide/ceria mixed systems.Barium oxide/ceria mixed systems will first be investigated without and then with support (Al2O3) and nobel metal (Pt) component. To elucidate the NOx storage mechanism for the different ceria containing materials, the in situ Raman/FTIR methodology developed in the first founding period will be employed. This approach combines the potential of in situ Raman spectroscopy with quantitative FTIR gas phase analysis at the outlet of the in situ Raman cell. These studies include the determination of the corresponding NOx storage capacities. Due to the complexity of ceria containing NOx storage reduction catalysts the in situ Raman characterization will be supported by detailed studies using X-ray photoelectron spectroscopy (XPS) partly in combination with Raman and und UV-Vis spectroscopy.As the stability of NOx storage reduction catalysts is strongly related to their susceptibility to sulfur poisoning one focus of the project is to investigate the influence of sulfur (as SO2). Besides, the influence of other components with large volume fractions in the exhaust gas (CO2, H2O) will be studied. Their presence may significantly influence the NOx storage mechanism as demonstrated for H2O during the first funding period.