Oxidation Chemistry on Transition-Metal Doped Rare Earth Oxide Surfaces: Factors Determining Selectivity for the Oxidative Coupling of Methane

在这个项目中，佛罗里达大学的Jason Weaver和Helena Hagelin-Weaver博士正在研究过渡金属掺杂剂如何改变稀土氧化物（REO）催化的氧化化学，特别关注碳氢化合物的氧化。特别感兴趣的是使用金属掺杂的REO作为催化剂，以有效地促进甲烷（OCM）氧化偶联为有价值的两碳（C2）产物，同时避免甲烷完全氧化为二氧化碳（CO2）和水（H2O）。开发商业上可行的OCM催化剂可以使得能够更有效地利用天然气资源，并且因此具有显著的经济和环境影响。该项目旨在推进对REO催化剂对部分氧化反应与完全氧化反应的选择性的基本理解，并实现设计具有理想和可调节性能的金属掺杂REO催化剂的合理方法。通过掺杂不同类型的过渡金属来可预测地改变氧化物的催化性能的能力可以在工程催化剂中提供显著的灵活性，用于广泛的应用，包括化学合成，污染控制和能源技术。该项目包括与德国和瑞典的研究人员合作，为研究生提供在外国实验室培训和在同步加速器设施进行实验的机会。本科生也参与了这项研究，代表性不足的少数民族通过调查人员参与大学少数民族导师计划和女工程师协会招募，在这个由化学催化计划资助的项目中，佛罗里达大学的Jason Weaver博士和Helena Hagelin-Weaver博士正在研究模型稀土氧化物（REO）薄膜和高表面-区域催化剂，特别侧重于系统地表征过渡金属掺杂对REO表面促进的氧化化学的影响。REO表现出良好的催化性能，用于各种化学转化，包括部分和完全氧化反应。然而，与二氧化铈作为一个一般的例外，REO表面化学的机械细节和决定催化选择性的因素只在有限的程度上理解。该项目的重点是钐和铽作为有效的不可还原和可还原的稀土氧化物的代表性例子，分别，并澄清促进甲烷（OCM）的氧化偶联C2产品，而不是完全氧化的因素。一个综合的方法，涉及过渡金属掺杂REO薄膜在超真空（UHV）和表征纳米晶体REO催化剂在更现实的反应条件下的模型研究，目的是建立明确的桥梁，在理解跨材料和压力鸿沟。该项目的主要目标是对掺杂不同金属的REO表面的结构/电子性质和化学选择性之间的关系有新的了解，并阐明现实条件下表面化学的机理方面。该项目涉及与德国和瑞典的研究人员合作，并为学生提供在外国实验室进行培训和在同步加速器设施进行实验的机会。本科生也参与了这项研究，通过PI和共同PI参与大学少数民族辅导方案和女工程师协会，招募了代表性不足的少数民族。

Oxidation Chemistry on Transition-Metal Doped Rare Earth Oxide Surfaces - Factors Determining Selectivity for the Oxidative Coupling of MethaneIn this project, Drs. Jason Weaver and Helena Hagelin-Weaver at the University of Florida are investigating how transition-metal dopants modify the oxidation chemistry catalyzed by rare earth oxides (REOs), focusing particularly on the oxidation of hydrocarbons. Of particular interest is the use of metal-doped REOs as catalysts to efficiently promote the oxidative coupling of methane (OCM) to valuable two carbon (C2) products, while avoiding the complete oxidation of methane to carbon dioxide (CO2) and water (H2O). Developing a commercially viable OCM catalyst may enable the more effective utilization of natural gas resources, and thus have significant economic and environmental impacts. The project aims to advance the basic understanding of the selectivity of REO catalysts toward partial vs. complete oxidation reactions, and to enable rational approaches for designing metal-doped REO catalysts with desirable and adjustable properties. The ability to predictably modify the catalytic properties of an oxide by doping with different types of transition metals could afford significant flexibility in engineering catalysts for a wide-range of applications, including chemical synthesis, pollution control, and energy technologies. The project includes collaboration with researchers in Germany and Sweden that provide opportunities for graduate students to train in foreign laboratories and perform experiments at synchrotron facilities. Undergraduate students are also involved in this research, and underrepresented minorities are recruited through the investigators' participation in the University Minority Mentoring Program and in the Society of Women Engineers.In this project funded by the Chemical Catalysis Program, Drs. Jason Weaver and Helena Hagelin-Weaver at the University of Florida are investigating the properties of model rare earth oxide (REO) thin films and high surface-area catalysts, focusing particularly on systematically characterizing the effects that transition-metal doping have on the oxidation chemistry promoted by REO surfaces. REOs exhibit favorable catalytic performance for a diverse set of chemical transformations, including both partial and complete oxidation reactions. However, with ceria as a general exception, mechanistic details of REO surface chemistry and the factors determining catalytic selectivity are understood only to a limited extent. The project focuses on samaria and terbia as representative examples of effectively irreducible and reducible REOs, respectively, and on clarifying factors that promote the oxidative coupling of methane (OCM) to C2 products rather than complete oxidation. A combined approach is employed that involves model studies of transition-metal doped REO thin films in ultrahigh vacuum (UHV) and characterization of nano-crystalline REO catalysts under more realistic reactive conditions, with the aim to establish clear bridges in understanding across the materials and pressure divides. Key goals of the project are to develop new understanding of the relations between structural/electronic properties and the chemical selectivity of REO surfaces doped with different metals and to illuminate mechanistic aspects of the surface chemistry under realistic conditions. The project involves collaboration with researchers in Germany and Sweden and provides opportunities for students to train in the foreign laboratories and perform experiments at synchrotron facilities. Undergraduate students are also involved in this research, and underrepresented minorities are recruited through the PI's and co-PI's participation in the University Minority Mentoring Program and in the Society of Women Engineers.