SusChEM: Single Molecule Studies of Aldol Condensation on Heterogeneous Catalysts

将可再生生物质资源转换为燃料提供了一种途径，可持续地满足社会日益增长的能源需求，而不依赖化石燃料。然而，从生物质中最容易提取的化合物与从加工石油或页岩中获得的传统碳氢化合物有很大不同。一个主要的区别是，大多数生物质衍生的化合物比碳氢燃料小，需要催化反应从原始化合物生成更大的分子。在这些反应中，催化剂是一种固体薄膜，包含有助于反应效率的化学物质，但本身并不在反应中消耗。Hohn博士和Higgins博士正在研究一个这样的反应--羟醛缩合反应，以了解什么催化特性最适合这项任务。为了实现这一点，他们遵循发生在催化剂薄膜上的发光反应，他们沿着薄膜表面产生催化性能的梯度。观察薄膜的哪些部分发出最亮的光提供了关于最活跃的催化中心类型的信息，并使研究小组能够设计改进的催化剂。正在以多种方式传播研究成果，包括通过在科学会议和同行评议的出版物上发表演讲。霍恩博士还将研究成果纳入K-12学生的外展活动中，而希金斯博士则将研究成果引入显微镜教科书和研究生级别的化学课堂。在化学系化学催化项目的资助下，堪萨斯州立大学的霍恩博士和希金斯博士正在发展对羟醛缩合反应活性的催化性质的基本理解。他们正在应用单分子方法来同时测量酸碱性质和薄膜上的羟醛缩合活性，薄膜上含有酸碱密度的梯度。通过这些测量，他们将羟醛缩合反应中的催化活性与酸/碱中心的强度和密度关联起来。该团队应用表面表征方法，包括X射线光电子能谱(XPS)和拉曼图谱研究，以加强单分子表征研究。此外，Hohn博士和Higgins博士通过在分子水平上制备混合了酸碱中心的薄膜，以及通过宏观距离分离酸碱中心的薄膜，将Aldol缩合反应中的催化活性与酸碱中心的接近程度关联起来。除了定期在同行评议的文献和会议上发表结果，霍恩博士还将这项研究的各个方面纳入堪萨斯州立大学的外展项目活动中，以加强招收来自代表性不足群体的学生进入科学和工程专业，而希金斯博士正在将选定的结果引入研究生水平的课程和化学显微镜教科书。

Converting renewable biomass resources to fuels provides a way to meet society's growing energy demands sustainably without reliance on fossil fuels. However, the compounds most easily extracted from biomass are quite different from conventional hydrocarbons obtained from processing petroleum or shale. One major difference is that most biomass-derived compounds are smaller than hydrocarbon fuels, necessitating catalytic reactions to build larger molecules from the original compounds. In these reactions, the catalyst is a solid film comprising chemicals that aid the efficiency of the reaction, but are not themselves consumed in the reaction. Drs. Hohn and Higgins are studying one such reaction, aldol condensation, to understand what catalytic properties are best suited to this task. To accomplish this, they follow a light-emitting reaction occurring on a catalyst film that they create with a gradient of catalytic properties along the film surface. Observing which parts of the film emit the brightest light provides information on the types of catalytic sites that are most active and allows the team to design improved catalysts. Research results are being disseminated in several ways, including through presentations at scientific conferences and peer reviewed publications. Dr. Hohn is also incorporating research results into outreach activities for K-12 students, while Dr. Higgins is introducing research results into a textbook on microscopy and into a graduate-level chemistry class.With funding from the Chemical Catalysis Program of the Chemistry Division, Drs. Hohn and Higgins of Kansas State University are developing a fundamental understanding of the catalytic properties responsible for activity in aldol condensation. They are applying single molecule methods to simultaneously measure acid/base properties and aldol condensation activity on thin films incorporating gradients in acid/base site densities. With these measurements, they are correlating catalytic activity in aldol condensation with the strengths and densities of the acid/base sites. The team applies surface characterization methods, including x-ray photoelectron spectroscopy (XPS) and Raman mapping studies, to augment the single molecule characterization studies. In addition, Drs. Hohn and Higgins correlate catalytic activity in aldol condensation with acid/base site proximity by preparing films with acid and base sites mixed at the molecular level and films where acid and base sites are separated by macroscopic distances. Along with regular publication of the results in the peer reviewed literature and presentation at conferences, Dr. Hohn is incorporates aspects of the research into activities for outreach programs at Kansas State University to enhance the recruitment of students from under-represented groups into science and engineering, while Dr. Higgins is introducing selected results into a graduate-level course and a textbook on chemical microscopy.