SusChEM: Collaborative Research: Surface Reaction of Oxygenates on Lewis Acidic Metal Oxides

该项目的总体目标是设计路易斯酸催化剂，用于将糖(从生物可再生能源发酵中容易获得)转化为增值化学品。金属氧化物催化剂，如二氧化钛和钼氧化物，对糖的许多反应都具有活性，但对各种催化剂的组成和结构与其产生的产品之间的关系缺乏了解。该项目将查明不同催化剂产生不同产品的原因，从而促进为生产特定目标化合物而优化的催化剂的设计，包括乙二醇和乳酸等高价值生物可再生产品。该项目将使用低成本的催化剂材料，这将为经济上可行的路线铺平道路，使有价值的化工原料能够持续生产。最近的研究表明，关键异构化和复古羟醛路线的相对速率受到催化剂组成的强烈影响。将结合模型表面的表面科学实验、高表面积氧化物的光谱和动力学研究以及密度泛函理论计算来确定表面结构和组成如何影响单个基本反应步骤的速度。具体地说，这项研究将集中于糖转化的基元反应如何受到各种表面性质的影响，包括电子性质(如Lewis酸强度和轨道填充)和几何因素(如空间位阻或合作活性中心的接近程度)。分离关键的基本步骤，包括激活或形成碳水化合物中的O-H、C-H、C-O和C-C键，将能够通过研究方法研究适当的探针反应物的表面反应。实验表面科学研究将提供有关不同表面上的基本台阶势垒和反应中间体的新信息。计算将有助于机理的发展，但更重要的是将用于评估表面中间吸附能和反应势垒的趋势如何与电子性质有关。操纵面光谱研究将提供一个新的理解，了解复杂的表面，如非理想表面和溶剂的存在，如何扰乱表面中间体的结构和稳定性，为改进反应模型提供关键反馈，最终将用于设计改进的催化剂。该项目将建立在调查人员培训研究生和本科生，包括来自传统代表性不足群体的学生的记录的基础上。该项目将允许博士生和本科生参与不同实验室之间的轮换，以培养从不同角度解决同一总体问题的能力。社区外展活动包括与亚特兰大地区的一家博物馆接触，以及为K-12学生提供项目。

The overall goal of the project is to enable the design of Lewis acid catalysts for conversion of sugars (readily obtained from fermentation of biorenewables) to value-added chemicals. Metal oxide catalysts, such as titanium dioxide and molybdenum oxides, are active for a number of reactions of sugars, but understanding is lacking regarding relationships between the composition and structure of various catalysts and the products they produce. The project will identify the reasons why different catalysts produce different products, and thus facilitate the design of catalysts that are optimized for the production of specific target compounds, including high-value biorenewable products such as ethylene glycol and lactic acid. The project will utilize low-cost catalyst materials that will pave the way to economically viable routes for enabling sustainable production of valuable chemical feedstocks.Recent work has shown that the relative rates for key isomerization and retro aldol pathways are strongly influenced by the catalyst composition. A combination of surface science experiments on model surfaces, spectroscopic and kinetic studies of high-surface area oxides, and density functional theory calculations will be employed to identify how surface structure and composition affect the rates of individual elementary reaction steps. Specifically, the research will focus on how elementary reactions for sugar conversion are affected by various surface properties, including electronic properties (such as Lewis acid strength and orbital filling) and geometric factors (such as steric hindrance or proximity of cooperative active centers). Isolation of key elementary steps, which include activation or formation of O-H, C-H, C-O, and C-C bonds in carbohydrates, will be enabled by studying the surface reactions of appropriate probe reactants across the research approaches. Experimental surface science studies will provide new information on elementary step barriers and reaction intermediates on different surfaces. Computation will assist in mechanism development, but more importantly will be used to assess how trends in surface intermediate adsorption energies and barriers for their reactions are related to electronic properties. Operando spectroscopy investigations will provide a new understanding of how complexities, such as non-ideal surfaces and the presence of a solvent, perturb the structure and stability of surface intermediates, providing key feedback for refinement of reaction models that will ultimately be used to design improved catalysts. The project will build on the investigators' track record of training graduate and undergraduate students including students from traditionally underrepresented groups. The project will allow both PhD and undergraduate students to participate in rotations among the different laboratories to develop an ability to address the same overall problem from different angles. Community outreach activities include engagement with an Atlanta-area museum and programs for K-12 students.