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

摘要#1258715-Fabio Ribeiro#1258690-William Schneider#1258717-Jean-Sabin McEwen缺乏实用且经济实惠的稀薄NOx后处理是交通运输中广泛采用节油柴油发动机和稀燃汽油发动机的主要障碍。日益严格的NOx排放标准要求NOx到氮气的转化率达到或超过标准驱动周期内平均90%，甚至更高的瞬时转化率，以补偿冷启动和瞬时运行。这些高转化率在贫氧条件下很难实现，在贫氧条件下，NOx必须与压倒性过剩的O2竞争有限数量的还原剂。稀薄NOx捕集器可以实现必要的NOx转化效率，但目前的形式存在许多运营和成本问题。氮氧化物选择性催化还原(SCR)为稀有氮氧化物的后处理提供了一种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，该催化剂促进NOx与还原剂(如尿素、NH3或碳氢化合物)的反应，选择性地生成氮气，而不是还原剂与O2的竞争反应。在铜交换的沸石分子筛上，氨的选择性催化还原是稀薄NOx还原的最新技术，使稀燃发动机的燃油效率成为可能。虽然这些材料只在一小部分运输市场上用于商业用途，但随着它们对不同的SCR条件做出反应，特别是当它们积累失活的硫物种时，它们的结构和催化行为会以不可预测的方式发生变化。康明斯对这些催化剂的实际应用表明，它们在低温下的性能下降的方式无法用之前发表的老化机制来解释。NOx SCR催化剂的合理改进和有效应用的主要障碍是对催化剂的基本结构和催化化学缺乏坚实的基础了解。应国家科学基金会和美国能源部关于先进内燃机的联合征集，提出了一种填补这一知识空白以获得最高SCR催化剂性能的方法。该机构的联合奖项是通过NSF化学、生物工程、环境和运输系统部门及其催化和生物催化计划颁发给一个多学科团队，该团队由普渡大学的Fabio H.Ribeiro、W.Nicholas Delgass和Rajamani Gounder教授、华盛顿州立大学的Jean-Sabin McEwen教授和圣母大学的William F.Schneider教授、Argonne国家实验室的Jeffrey T.Miller博士、太平洋西北国家实验室的Charles H.F.Peden博士组成。NSF的Aleksey Yezerets博士也为这个团队提供了支持，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，并有成功合作的可靠记录。为了显著改进目前的催化剂材料，在排放限制内优化发动机效率，并避免失活，建立一个在所有操作条件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取得了世界级的卓越成就，这些学科必须结合在一起，以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催化剂系统的预测模型的基础，并为进一步的催化剂系统改进奠定基础。尽管参与这个项目的学生将专门从事研究的特定方面，但与整个团队和团队频繁地举行电话会议，前往国家实验室进行专门的实验，将提供广泛的经验，并直接接触到各种实验和催化研究前沿的分子理论之间相互作用的重要性。因此，这个多机构和多样化的团队将培养研究生和博士后，使他们在应用催化技术解决能源效率和环境问题方面达到最高水平。它还将为高中生和本科生提供决定职业生涯的教育机会。对于高中生和教育工作者，普渡大学已经为对科学和工程感兴趣的学生开发了一个动手演示文稿。PI们打算将这项工作的分子观点添加到演讲中，并向印第安纳州各地的高中发表演讲，并将这一观点带到普渡大学和巴黎圣母院夏季举办的许多科学和工程夏令营。在大学研究小组和康明斯工业实习中工作的本科生也将受益于广泛的科学接触和独特的方法，这种方法将详细的基本理解与重要实际问题的解决联系起来。

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.