NSF/DOE Advanced Combustion Engines: Collaborative Research: GOALI: Understanding NOx SCR Mechanism and Activity on Cu/Chabazite Structures throughout the Catalyst Life Cycle

缺乏一种实用且具有成本效益的精益氮氧化物后处理技术是阻碍高效柴油和稀燃汽油发动机广泛应用于交通运输的主要障碍。越来越严格的氮氧化物排放标准要求在标准驱动循环中，氮氧化物转化为氮气的平均转化率达到或超过90%，甚至更高的瞬时转化率，以补偿冷启动和瞬态运行。这些高转化率在稀薄条件下很难实现，在稀薄条件下，NOx必须与过量的O2竞争有限数量的还原剂。精益氮氧化物捕集器可以实现必要的氮氧化物转换效率，但在目前的形式下存在许多操作和成本问题。氮氧化物选择性催化还原（SCR）为减少氮氧化物后处理提供了更令人满意的解决方案。在这种方法中，通常的转化器催化剂被一种催化剂取代，这种催化剂促进NOx与还原剂（如尿素、NH3或碳氢化合物）的反应，在还原剂与O2的竞争反应中选择性地产生N2。在cu交换的chaab沸石沸石上用氨选择性催化还原是最先进的稀薄氮氧化物还原技术，可以提高稀薄燃烧发动机的燃油效率。虽然这些材料在运输市场的一小部分被商业化使用，但它们的结构和催化行为会以不可预测的方式发生变化，因为它们会对不同的SCR条件做出反应，特别是当它们积累失活硫种时。这些催化剂在康明斯的实际应用表明，它们在低温下的性能下降的方式是以前发表的老化机制无法解释的。合理改进和有效应用NOx SCR催化剂的主要障碍是缺乏对潜在催化剂结构和催化化学的牢固基础认识。根据美国国家科学基金会和美国能源部关于先进内燃机的联合招标，提出了一种填补这一知识空白的方法，以实现SCR催化剂的最大性能。该联合机构奖通过美国国家科学基金会化学、生物工程、环境和运输系统部门及其催化和生物催化项目颁发给一个由普渡大学Fabio H. Ribeiro教授、W. Nicholas Delgass教授和Rajamani Gounder教授组成的多学科团队；华盛顿州立大学教授Jean-Sabin McEwen；圣母大学的William F. Schneider教授；阿贡国家实验室Jeffrey T. Miller博士；太平洋西北国家实验室Charles H. F. Peden博士；该团队在NOx催化和催化科学方面拥有多年的工业、国家实验室和学术经验，并有成功的合作记录，nsf GOALI也为该团队提供支持。为了大幅改进现有的催化剂材料，在排放限制下优化发动机效率，并避免失活，在所有操作条件下和整个生命周期中建立催化剂性能的原子和分子详细模型至关重要。该团队在各种实验和理论学科方面具有世界一流的卓越水平，必须将这些学科结合起来，才能达到对该反应系统的动态化学和催化性质的原子水平的理解，这将构成该SCR催化剂系统和进一步催化剂系统改进的预测模型的基础。虽然从事该项目的学生将专注于研究的特定方面，但与整个团队的频繁远程会议以及前往国家实验室进行专业实验的小组将提供广泛的经验，并直接暴露在催化研究前沿的各种实验和分子理论之间相互作用的重要性。因此，这个多机构和多元化的团队将培养研究生和博士后，使他们能够在催化技术应用的最高水平上解决能源效率和环境问题。它还将为高中生和本科生提供职业定义教育机会。针对高中学生和教育工作者，普渡大学已经开发了一个动手演示，以吸引对科学和工程感兴趣的学生。pi们打算将这项工作的分子观点加入到报告中，并在印第安纳州的高中进行讲座，并将这种观点带到普渡大学和圣母大学夏季举办的许多科学和工程营地。在大学研究小组和康明斯工业实习的本科生也将受益于广泛的科学接触和独特的方法，将详细的基本理解与重要实际问题的解决方案联系起来。

ABSTRACT#1258715 - Fabio Ribeiro#1258690 - William Schneider#1258717 - Jean-Sabin McEwenThe lack of a practical and cost-effective lean NOx aftertreatment is the major obstacle to the widespread adoption of fuel-efficient diesel and lean-burn gasoline engines for transportation. Increasingly stringent NOx emissions standards demand that NOx conversion to N2 reach or exceed 90% averaged over standard drive cycles, and even higher instantaneous conversions to compensate for cold startup and transient operation. These high conversions are very difficult to achieve under lean conditions, in which NOx must compete with an overwhelming excess of O2 for a limited amount of reductant. Lean NOx traps can achieve the necessary NOx conversion efficiencies, but have many operational and cost issues in their current forms. NOx selective catalytic reduction (SCR) provides a much more satisfactory solution to lean NOx aftertreatment. In this approach the usual converter catalyst is replaced with a catalyst that promotes reaction of NOx with a reductant, such as urea, NH3, or hydrocarbons, to produce N2 selectively over the competing reactions of reductant with O2.The selective catalytic reduction with ammonia on Cu-exchanged chabazite zeolites is the state-of-the-art for lean NOx reduction and enables access to the fuel efficiency of lean burn engines. Although these materials are used commercially in a small segment of the transportation market, their structure and catalytic behavior changes in unpredictable ways as they respond to varying SCR conditions and in particular as they accumulate deactivating sulfur species. Real-world application of these catalysts at Cummins reveals that their performance at low temperatures is diminished in ways not explained by previously published aging mechanisms. The primary obstacle to the rational improvement and effective application of NOx SCR catalysts is the lack of a firm fundamental understanding of the underlying catalyst structure and catalytic chemistry.An approach to filling this knowledge gap to lead to maximum SCR catalyst performance has been proposed in response to the joint National Science Foundation and Department of Energy solicitation on Advanced Combustion Engines. The joint Agency award is made through the NSF Chemical, Bioengineering, Environmental and Transport Systems Division and its Catalysis & Biocatalysis Program to a multi-disciplined team made up of Professors Fabio H. Ribeiro, W. Nicholas Delgass, and Rajamani Gounder at Purdue University; Prof. Jean-Sabin McEwen at Washington State University; and Prof. William F. Schneider at University of Notre Dame; Dr. Jeffrey T. Miller, Argonne National Laboratory; Dr. Charles H. F. Peden, Pacific Northwest National Laboratory; and Dr. Aleksey Yezerets, Cummins Inc.NSF GOALI support is also provided to this team that has many years of combined industrial, National Laboratory and academic experience in NOx catalysis and catalysis science and a proven record of successful collaboration.To dramatically improve the present catalyst materials, to optimize engine efficiency within emission constraints, and to circumvent deactivation, an atomic and molecularly detailed model of catalyst performance under all operating conditions and throughout the life cycle is essential. This team brings world-class excellence in the variety of experimental and theoretical disciplines that must be combined to reach the atomic-level understanding of the dynamic chemical and catalytic properties of this reaction system, which will form the basis of a predictive model for this SCR catalyst system and for further catalyst system improvements. Though the students working on this project will specialize in particular aspects of the research, frequent teleconferences with the entire team and groups traveling to the National Labs to do specialized experiments will provide broad experience and direct exposure to the importance of the interplay between various experiments and molecular theory at the frontier of catalysis research. Thus, this multi-institutional and diverse team will prepare graduate students and postdocs to operate at the highest levels in application of catalysis to the solution of energy efficiency and environmental problems. It will also provide career-defining educational opportunities to high school and undergraduate students. For high school students and educators, Purdue has already developed a hands-on presentation to interest students in science and engineering. The PIs intend to add the molecular view of this work to that presentation and deliver lectures to high schools across Indiana and to bring this view to the many science and engineering camps that run at Purdue and Notre Dame during the summer. Undergraduates working in the university research groups and in industrial internships at Cummins will also benefit from the breadth of scientific exposure and the unique approach that connects detailed fundamental understanding to the solution of important practical problems.