In-situ Investigation of Model Multi component Catalyst Systems

虽然催化剂被要求解决越来越具有挑战性的排放控制需求，但进展受到主要基于现象学的“试错”方法的催化系统的开发的阻碍。在该计划中，来自麻省理工学院和拜罗伊特大学（UBT）的合作者将在现实的操作条件下应用跨学科方法，利用多种表征工具，以详细了解催化剂系统中所有组分的行为和相互作用（载体、存储组分、贵金属）。在此背景下，本建议集中于基于（Ce，M）O2-6（MIT）和BaCO 3（UBT）的模型催化剂配方，其分别为各种催化剂概念提供氧和NOx储存/释放能力。氧/氮氧化物存储和支持材料将被整合在三个-以通过气相或溶液方法沉积到氧化物衬底上的膜为特征的层布置允许系统地控制表面积、三相边界和扩散长度。通过微球模板化和喷墨印刷（MIT），将实现表面积和受控的介孔和纳米孔。通过这些手段，可以控制存储材料内的氧扩散率，并且隔离其对整体性能的影响。存储材料的缺陷化学和氧交换性能，通过固溶体形成/掺杂剂进行改性，将通过库仑滴定，电子/离子电导率，复阻抗和晶体微量天平方法进行检查。此外，两个实验室还将进行表面敏感测量，包括功函数（MIT）、XPS和DRIFT（UBT）。差流反应器研究（UBT）将提供所需的整体催化剂性能输入，而低热质量陶瓷微热板将允许汽车排气中经历的编程快速热偏移。在该项目的最后阶段，单个组件的结果将被整合到一个更复杂的模型系统中，研究氧气和NOx存储组件之间的相互作用，同时考虑到关键参数，如二氧化铈/BaCO 3比，空间分布，形态和金属负载。将开发和测试描述各种催化剂系统组分相互作用的模型。模型系统的整体电响应将是特别感兴趣的，不仅作为一种调查工具，而且作为一种手段，诊断催化剂的性能在原位。合作的一个核心部分将是扩大学生和工作人员的交流，学习新的实验和建模方法，应用各自实验室的独特设施，并从全球角度深入了解如何进行研究。更广泛的影响：催化剂在过去30年中为减少90%以上的汽车排放发挥了核心作用，但进展在很大程度上受到现象学的“试错”方法的影响。结果，抑制了用于使用于车载诊断应用的催化剂的建模和优化合理化的手段。该项目旨在更好地了解催化剂材料的性质及其与基质和气体的相互作用。这样的理解将推进催化剂科学，并提高催化剂的工程能力，以改善功能。这也有可能影响广泛的商业战略行业，包括石化催化裂化，蒸汽重整，标准化学品（氨，硫酸）的合成和燃料电池电极，所有这些都依赖于非均相催化剂。鉴于对环境的关注，这项工作非常适合有趣的年轻学生，K-12学生的外展计划将从麻省理工学院目前的水平扩大。同样，该计划将用于吸引本科生参加该计划。

While catalysts are being called upon to address ever more challenging emission control needs, progress is hindered by development of catalytic systems based largely on a phenomenological, “trial-and-error” approach. In this program, the collaborators from MIT and the University of Bayreuth (UBT) will apply an interdisciplinary approach utilizing multiple characterization tools, under realistic operating conditions, to achieve a detailed knowledge of the behavior and interplay of all the components within the catalyst system (support, storage component, noble metal). In this context, the present proposal focuses on model catalyst formulations based on (Ce,M)O2-6 (MIT) and BaCO3 (UBT) which provide the oxygen and NOx storage/release capacity respectively for various catalysts concepts.Model structures composed of noble metal, oxygen/NOx storage and support materials will be integrated in three-layer arrangements featuring films deposited by vapor or solution methods onto oxide substrates allowing for systematic control of surface area, triple phase boundary and diffusion lengths. Surface area and controlled meso- and nano-porosity will be achieved by microsphere templating and ink-jet printing (MIT). By these means, oxygen diffusivity within the storage material can be controlled, and its impact on overall performance isolated. The defect chemistry and oxygen exchange properties of the storage materials, to be modified by solid solution formation/dopants, will be examined by coulometric titration, electronic/ionic conductivity, complex impedance and crystal microbalance methods. Additionally, surface sensitive measurements, including work function (MIT), XPS and DRIFT (UBT), will be applied in the two laboratories. Differential flow reactor studies (UBT) will provide needed overall catalyst performance input, while low thermal mass ceramic micro hot-plates will allow for programmed rapid thermal excursions of the type experienced in automotive exhausts. In the final stage of the project, results for the single components will be integrated into a more complex model system studying interactions between oxygen and NOx storage components, taking into account key parameters such as ceria/BaCO3 ratio, spatial distribution, morphology, and metal loading. Models describing the interactions of the various catalyst system components will be developed and tested. The overall electrical response of the model system will be of particular interest, not only as an investigative tool, but also as a means of diagnosing catalyst performance in situ. A central component of the collaboration will be extended exchanges of students and staff to learn new experimental and modeling methods, apply the unique facilities of the respective labs and provide insight into how research is approached from a global perspective.Broader Impact:Catalysts have played a central role in reducing automotive emissions by over 90% over the past three decades but progress is slowed by largely a phenomenological, “trial-and-error” approach. As a consequence, means for rationalizing the modeling and optimization of catalysts for onboard diagnosis applications has been inhibited. This project aims to obtain an improved understanding of the catalyst materials properties and their interactions with substrate and gases. Such understanding will advance the science of catalysts as well as improve the ability to engineer catalysts towards improved functionality. This has the potential for impacting, as well, a broad range of commercially strategic industries including petrochemical catalytic cracking, steam-reforming, synthesis of standard chemicals (ammonia, sulfuric acid), & fuel cell electrodes, all of which depend on heterogeneous catalysts. Given the focus on environment, this work is ideally suited for interesting young students and an outreach program for K-12 students will be expanded from present levels at MIT. Likewise, the program will be used to attract undergraduates to the program.