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

该项目的总体目标是设计Lewis酸催化剂，将糖（很容易从生物可再生能源发酵中获得）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，对糖的许多反应都有活性，但对各种催化剂的组成和结构与它们产生的产物之间的关系还缺乏了解。该项目将确定不同催化剂产生不同产品的原因，从而促进催化剂的优化设计，以生产特定的目标化合物，包括高价值的生物可再生产品，如乙二醇和乳酸。该项目将使用低成本的催化剂材料，为实现有价值的化学原料的可持续生产铺平经济可行的道路。最近的研究表明，关键异构化和复古醛醇途径的相对速率受到催化剂组成的强烈影响。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，将确定表面结构和组成如何影响单个基本反应步骤的速率。具体来说，研究将集中于糖转化的基本反应如何受到各种表面性质的影响，包括电子性质（如刘易斯酸强度和轨道填充）和几何因素（如位阻或协同活性中心的接近性）。分离关键的基本步骤，包括碳水化合物中O-H、C-H、C-O和C-C键的激活或形成，将通过研究适当的探针反应物的表面反应来实现。实验表面科学的研究将为不同表面上的初级台阶障碍和反应中间体提供新的信息。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它们的反应的势垒的趋势如何与电子性质相关。Operando光谱研究将为复杂性（如非理想表面和溶剂的存在）如何干扰表面中间体的结构和稳定性提供新的理解，为改进反应模型提供关键反馈，最终用于设计改进的催化剂。该项目将以调查人员培训研究生和本科生的记录为基础，包括来自传统上代表性不足群体的学生。该项目将允许博士和本科生参与不同实验室之间的轮转，以培养从不同角度解决相同整体问题的能力。社区外展活动包括参与亚特兰大地区的博物馆和K-12学生的项目。

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.