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

缺乏实用且经济的稀燃NOx后处理是广泛采用燃料效率高的柴油和稀燃汽油发动机用于运输的主要障碍。越来越严格的NOx排放标准要求NOx转化为N2达到或超过标准驱动循环的平均90%，甚至更高的瞬时转化率以补偿冷启动和瞬态操作。这些高转化率在贫燃条件下非常难以实现，其中NOx必须与压倒性过量的O2竞争有限量的还原剂。贫NOx捕集器可以实现必要的NOx转化效率，但是在其当前形式下具有许多操作和成本问题。 NOx选择性催化还原（SCR）技术为稀燃NOx后处理提供了一种更为理想的解决方案。在该方法中，通常的转化器催化剂被促进NOx与还原剂（例如尿素、NH3或烃）的反应的催化剂代替，以相对于还原剂与O2的竞争反应选择性地产生N2。在Cu交换的菱沸石上用氨的选择性催化还原是稀燃NOx还原的最新技术，并且能够获得稀燃发动机的燃料效率。尽管这些材料在商业上用于运输市场的一小部分，但它们的结构和催化行为以不可预测的方式变化，因为它们响应于变化的SCR条件，特别是当它们积累失活硫物质时。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会以以前发表的老化机制无法解释的方式降低。NOx SCR催化剂的合理改进和有效应用的主要障碍是缺乏对催化剂结构和催化化学的基本理解，为了响应美国国家科学基金会和能源部关于先进燃烧发动机的联合征集，提出了一种填补这一知识空白以获得最大SCR催化剂性能的方法。联合机构奖是通过NSF化学，生物工程，环境和运输系统部门及其催化生物催化计划，以多学科的团队由教授法比奥H。Ribeiro，W.普渡大学的NicholasDelgass和RajamaniGounder教授，华盛顿州立大学的Jean-SabinMcEwen教授，和WilliamF. McEwen教授。圣母大学的施耐德博士;米勒，阿贡国家实验室; F.佩登，太平洋西北国家实验室;和康明斯公司的Aleksey Yezerets博士。NSF GOALI支持也提供给这个团队，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，并有成功合作的良好记录。为了显著改善现有催化剂材料，在排放限制范围内优化发动机效率，并避免失活，在所有操作条件下和整个生命周期中催化剂性能的原子和分子详细模型是必不可少的。该团队在各种实验和理论学科方面具有世界级的卓越性，这些学科必须结合起来，以达到对该反应系统的动态化学和催化特性的原子级理解，这将构成该SCR催化剂系统的预测模型的基础，并进一步改进催化剂系统。虽然从事该项目的学生将专注于研究的特定方面，但与前往国家实验室进行专业实验的整个团队和团体的频繁电话会议将提供广泛的经验，并直接接触到各种实验之间相互作用的重要性和催化研究前沿的分子理论。因此，这个多机构和多样化的团队将准备研究生和博士后在催化应用于解决能源效率和环境问题的最高水平上运作。它还将为高中和本科生提供职业定义教育机会。 对于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，以感兴趣的学生在科学和工程。 PI打算将这项工作的分子观点添加到演讲中，并在印第安纳州的高中进行演讲，并将这一观点带到夏季在普渡大学和圣母大学举办的许多科学和工程夏令营中。 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知识和独特的方法，将详细的基本理解与重要的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.