SusChEM: Investigation of a Core-Shell Redox Catalyst Platform for Oxidative Dehydrogenation of Ethane

该项目将研究乙烷氧化脱氢（ODH）生产乙烯-一种高容量的化学中间体。采用了一种新颖的方法，利用核壳催化剂设计与化学环氧化还原循环相结合，在不直接供氧的情况下实现ODH。这种结合的方法有可能消除从空气中分离氧气的昂贵且能源密集型的过程，同时也减少了碳排放。这项工作将为研究生和本科生提供多学科的教育机会，并为高中生和教师提供外展活动，以激发他们对STEM职业的兴趣。核壳型氧化还原催化剂是化学环反应中乙烷ODH的活性催化剂和有效的晶格氧离子供体。该工作计划测试了三个关键假设：1)在循环氧化还原模式下，化学和结构相容的伯胺（钴/铁）氧化物和钙钛矿可以组装成稳定的乙烷ODH核壳排列；2)通过调整混合离子电子导体（MIEC）壳层的金属阳离子氧化态和缺陷结构，可以定制核壳氧化还原催化剂的表面性质，使其在没有气态氧化剂的情况下成为乙烷ODH的高效催化剂；3)乙烷ODH反应主要发生在钙钛矿表面，通过改良的Mars-van Krevelen机制裂解C-H键。为了验证这些假设，将确定相兼容的核和壳材料，然后组装成核-壳粒子。将研究钙钛矿a位和b位取代对ODH活性和选择性的影响，并将其与壳材料的缺陷结构和阳离子氧化态相关联。动力学和力学方面将在颗粒和薄膜上进行研究，利用原位拉曼和FT-IR/DRIFTS，分子束反应堆与x射线光电子能谱仪和脉冲同位素研究来复制核壳和壳结构。这些研究可能会产生全新的材料和方案，可以显著提高天然气生产乙烯的效率，同时减少排放。

The project will investigate the oxidative dehydrogenation (ODH) of ethane to produce ethylene - a high volume chemical intermediate. A novel approach is employed that utilizes a core-shell catalyst design in combination with a chemical looping redox cycle to achieve ODH without direct feed of oxygen. The combined approach potentially eliminates a costly and energy-intensive process for separating oxygen from air, while also reducing carbon emissions. The work will provide multi-disciplinary educational opportunities for graduate and undergraduate students, as well as outreach activities to high school students and teachers for stimulating interest in STEM careers.The core-shell redox catalyst is both an active catalyst and an effective lattice oxygen ion donor for ethane ODH in a chemical-looping scheme. The work plan tests three key hypotheses: 1) Chemically and structurally compatible primary (cobalt/iron) oxides and perovskites can be assembled into a stable core-shell arrangement for ethane ODH under a cyclic redox mode; 2) The surface properties of the core-shell redox catalyst can be tailored by tuning the metal cation oxidation state and defect structure of the mixed ionic-electronic conductor (MIEC) shell, rendering a highly effective catalyst for ethane ODH in the absence of gaseous oxidants; 3) Ethane ODH reaction occurs primarily on the perovskite surface via homolytic C-H bond cleavage through a modified Mars-van Krevelen mechanism. To test these hypotheses, phase-compatible core and shell materials will be identified and then assembled into core-shell particles. The effects of perovskite A-site and B-site substitutions on ODH activity and selectivity will be investigated and correlated to the defect structure and cation oxidation state of the shell material. Kinetic and mechanistic aspects will be investigated over pellets and thin films replicating the core-shell and shell structures using in-situ Raman and FT-IR/DRIFTS, a molecular beam reactor coupled with an X-ray photoelectron spectrometer, and pulse isotope studies. The studies will potentially result in fundamentally new materials and schemes that can significantly improve the efficiency for ethylene production from natural gas while reducing emissions.