Formation, Structure and Reactivity of Redox Sites in High-Silica H-Zeolites

高硅 H 沸石中氧化还原位点的形成、结构和反应性

• 批准号: 0931059
• 负责人: Raul Lobo
• 金额: $ 30万
• 依托单位: University of Delaware
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-09-15 至 2013-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0931059&HistoricalAwards=false
• 关键词: Formation; Structure; Reactivity; Redox; Sites

0931059LoboRecent studies from the PI's group have shown that Brønsted acid sites (Si-OH-Al) on high-silica zeolites decompose thermally at temperatures above 550°C producing hydrogen. This reaction leads to a formal oxidation of the zeolite framework where some oxygen atoms change oxidation state from 2- to 1-. The observation of this homolytic decomposition of Brønsted acid sites is a very unexpected result and opens the possibility that some of what is believed to be acid catalysis at high temperatures in zeolites is in fact redox chemistry. The aim of this proposal is to establish if this redox chemistry can indeed have an effect on the selectivity and yield of hydrocarbon reactions in zeolites at high temperatures and to elucidate the molecular and electronic structure of these redox sites.Intellectual Merit: The PI will investigate the decomposition of Brønsted acid sites under inert and oxidative conditions using Mass-Spectrometry-Temperature-Programmed- Reaction techniques to determine the conditions that lead to the oxidative decomposition of the Brønsted acid sites. After decomposition, the samples will be investigated using X-ray absorption spectroscopy, high-field 27Al MAS NMR spectroscopy, inelastic neutron scattering and a number of optical spectroscopy techniques to clarify their molecular and electronic structure. Transient kinetic studies of simple alkanes will be used to evaluate the effect of these redox sites on hydrocarbon cracking. The successful completion of the proposed research program will open a new window of inquiry into the chemistry of zeolites. These findings could have implications for important catalytic processes such as fluidized catalytic cracking and enhanced fuel reforming on Rh/zeolite catalysts. Furthermore, the expected results could also help elucidate similar redox processes observed in quartz and other minerals that have remained unexplained for decades.Broad Impact: Three mechanisms are given to reach out to elementary and junior high-school students and to underrepresented groups to enhance their understanding of science and engineering and entice them to think about engineering as a professional future. First, on campus and at local schools a short talk will be given directed to elementary and junior-high school students communicating in lay terms the impact that zeolites have on our lives. This talk will be prepared and delivered several times a year as part of the outreach activities of the College of Engineering at UD. Second, the PI plans to participate in the Research Experiences for Teachers program organized by the college, a hands-on summer research program for high-school science and math teachers, by hosting one or two of these teachers in his laboratory each year. Finally, he plans to work with faculty in the department of Chemistry at Lincoln University, a predominantly African American institution located closely to the University of Delaware, to bring some of their senior undergraduate students to participate in the proposed project and other on-going research programs in his laboratory. He plans to use these collaborative Delaware-Lincoln research activities to lure students into the benefits of pursuing graduate research after the completion of their undergraduate degree.In addition to educating one graduate student using a rich and complex scientific problem, the PI will also involve two undergraduate students in the research described here. This will be done through the University Science and Engineering Scholars Program, one of the hallmarks of Undergraduate Research Program at UDEL where undergraduates work with individual faculty for two consecutive summers on a specific research project. Many of these students end up pursuing research thesis during their senior year.

0931059 Lobo PI小组的最新研究表明，高硅沸石上的布朗斯特酸位点（Si-OH-Al）在高于550°C的温度下热分解，产生氢气。该反应导致沸石骨架的形式氧化，其中一些氧原子将氧化态从2-变为1-。观察到这种布朗斯特酸位点的均裂分解是非常意外的结果，并且打开了这样的可能性，即在沸石中的高温下被认为是酸催化的一些物质实际上是氧化还原化学。该提案的目的是确定这种氧化还原化学是否确实能够对高温下沸石中烃反应的选择性和产率产生影响，并阐明这些氧化还原位点的分子和电子结构。PI将使用质谱-程序升温-质谱法研究Brønsted酸位点在惰性和氧化条件下的分解。确定导致布朗斯台德酸位点氧化分解的条件的反应技术。分解后，将使用X射线吸收光谱、高场27 Al MAS NMR光谱、非弹性中子散射和一些光谱技术对样品进行研究，以澄清其分子和电子结构。简单烷烃的瞬态动力学研究将用于评估这些氧化还原位点对烃类裂解的影响。拟议研究计划的成功完成将为沸石化学的研究打开一扇新的窗口。这些发现可能对重要的催化过程，如流化催化裂化和强化燃料重整铑/沸石催化剂的影响。此外，预期的结果还可以帮助阐明在石英和其他矿物中观察到的类似氧化还原过程，这些氧化还原过程几十年来一直无法解释。广泛的影响：三种机制，以达到小学和初中学生和代表性不足的群体，以提高他们对科学和工程的理解，并吸引他们考虑工程作为一个专业的未来。首先，在校园和当地学校，将针对小学和初中学生进行简短的演讲，用通俗的语言交流沸石对我们生活的影响。这个讲座将准备和交付一年几次，作为UD工程学院外联活动的一部分。其次，PI计划参加由学院组织的教师研究经验计划，这是一个针对高中科学和数学教师的暑期实践研究计划，每年在他的实验室接待一到两名教师。最后，他计划与林肯大学化学系的教师合作，这是一所主要的非裔美国人机构，靠近特拉华州大学，让他们的一些高年级本科生参加他的实验室的拟议项目和其他正在进行的研究计划。他计划利用这些特拉华-林肯合作研究活动来吸引学生在完成本科学位后从事研究生研究的好处。除了使用丰富而复杂的科学问题教育一名研究生外，PI还将让两名本科生参与此处描述的研究。这将通过大学科学与工程学者计划来完成，这是UDEL本科研究计划的标志之一，本科生将连续两个夏天与个别教师合作进行特定的研究项目。这些学生中的许多人最终在他们的高年级追求研究论文。