Catalytic Reactivity at the Metal-Solution Interface

摘要#1157829Davis，Robert J.技术影响：由氧化铝和二氧化硅载体上的金属纳米颗粒组成的负载型金属催化剂已被优化用于化石燃料的升级以及石化产品的生产。最近一些化学工艺向利用生物可再生原料的转变需要新的催化剂在液态水中具有活性，液态水是一种在基于化石燃料的工业中不常见的反应介质。水是一种非常低成本、高极性、环境友好的溶剂，其具有作为生物质催化转化的反应介质的巨大潜力。事实上，与碳氢化合物相比，来自生物质的许多分子是高度氧化的并且极性很强，并且可能分解而不是蒸发，从而消除了传统的转化选择。氧化物载体在水性反应介质中不稳定。因此，碳水化合物衍生原料的水相催化加工的新催化剂必须是化学界的优先兴趣。为了充分利用可再生原料，必须了解这些水相体系中的基本催化化学。弗吉尼亚大学的Robert J. Davis教授已经开始了这些研究，最近观察了催化剂表面甘油反应性的机制。这个新项目探索了催化活性位点的性质，并探测了两种金属催化剂系统上吸附的中间体的反应性，这两种金属催化剂系统与液态水中生物可再生分子的催化转化高度相关。多元醇在Au催化剂上氧化成二元酸和多元醇在Pt-Re催化剂上氢解成二元醇将通过模型纳米颗粒和薄膜催化剂的原位衰减全反射FTIR光谱来探测，并与负载型金属催化剂在高压间歇式和流动反应器中的性能进行比较。初步研究已经揭示了Au和Pt-Re催化剂体系在液态水中的独特反应性，但是这些体系起作用的基本机械原理仍然未知。这项研究将阐明金属-水界面的关键特征，然后可以推广到其他感兴趣的反应在水溶液中的系统。Davis打算将酸/碱化学的联合收割机概念与金属催化作用结合起来，解释在液态水中发生的催化反应，并阐明可用于合成下一代催化剂的设计原则。一项新的推广工作将涉及主要研究者参与最近在弗吉尼亚大学成立的一个名为NExT的组织（纳米和新兴技术）和一个新的非营利组织称为NextTech，它扩大了NExT的影响到其他大学，并在全国各地的高中形成初级分会。NExT和NextTech全年都与当地K-12学生互动，包括指导科学博览会项目、客座研讨会/演示和共同赞助的活动。PI将与当地一所高中互动，该高中最近增加了一个名为数学工程和科学学院的新项目，该项目将数学和科学教学结合起来，涉及真实的世界问题解决、协作和基于探究的学习。

ABSTRACT#1157829Davis, Robert J.Technical Impacts:Supported metal catalysts composed of metal nanoparticles on alumina and silica supports have been optimized for the upgrading of fossil fuels as well as the production of petrochemicals. The recent transition of some chemical processes to utilize biorenewable feedstocks requires new catalysts to be active in liquid water, a reaction medium that is not commonly found in the fossil fuel based industries. Water is a very low cost, highly-polar, environmentally benign solvent that has great potential as a reaction medium for catalytic transformations of biomass. Indeed, many molecules derived from biomass are highly-oxygenated and quite polar compared to hydrocarbons and are likely to decompose rather than vaporize, thus eliminating the traditional conversion options. The oxide supports are not stable in the aqueous reaction medium. Therefore, new catalysts for aqueous-phase catalytic processing of carbohydrate-derived feedstocks must be a priority interest in the chemical community. The fundamental catalysis chemistry in these aqueous systems must be understood to make best use of the renewable feedstocks under consideration.Professor Robert J. Davis of the University of Virginia has begun these investigations, most recently observing the mechanisms of glycerol reactivity at catalyst surfaces. This new project explores the nature of the catalytic active site and probes the reactivity of adsorbed intermediates on two metal catalyst systems that are highly relevant to the catalytic transformation of biorenewable molecules in liquid water. The oxidation of polyols to diacids on Au catalysts and the hydrogenolysis of polyols to diols on bimetallic Pt-Re catalysts will be probed by in-situ attenuated total reflectance FTIR spectroscopy of model nanoparticle and thin film catalysts and compared to the performance of supported metal catalysts in high pressure batch and flow reactors. Preliminary research has revealed unique reactivity of both Au and Pt-Re catalyst systems in liquid water but the fundamental mechanistic principles by which these systems function are still unknown. This study will elucidate the key features of the metal-water interface which may then be generalized to other reactions of interest in aqueous systems. Davis intends to combine concepts of acid/base chemistry together with catalysis by metals to explain the catalytic reactions that occur in liquid water and to elucidate design principles that can be utilized for the synthesis of next generation catalysts.Education and Outreach Impacts: A new outreach effort will involve participation of the principal investigator in a recently-formed organization created at the University of Virginia called NExT (for Nano and Emerging Technologies) and a new non-profit organization called NextTech, which broadens the impact of NExT to other universities and forms junior chapters at high schools across the country. NExT and NextTech engage local K-12 students throughout the year and include mentoring science fair projects,guest seminars/demos, and co-sponsored events. The PI will interact with a local high school that has recently added a new program called the Math Engineering and Science Academy, that combines teaching in math and science to involve real world problem solving, collaboration and inquiry-based learning.