Collaborative Research: The role of oxide overlayers on adsorbate migration and metal sintering in reactions of CO2

合作研究：氧化物覆盖层对 CO2 反应中吸附物迁移和金属烧结的作用

• 批准号: 2152391
• 负责人: Kerry Dooley
• 金额: $ 30.23万
• 依托单位: Louisiana State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-10-01 至 2025-09-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2152391&HistoricalAwards=false
• 关键词: Collaborative; Research; role; oxide; overlayers

Combustion of natural gas (chiefly comprised of methane, i.e., CH4) provides a major portion of our nation’s energy needs. Although methane is a relatively “clean” fossil fuel, its combustion produces carbon dioxide (CO2) which constitutes the major component of greenhouse gas (GHG) emissions. Methane can also be reacted with steam (H2O) to produce carbon monoxide (CO) and hydrogen (H2) in a process known as methane steam reforming. The product CO and H2 gases are further reacted to produce a wide range of fuels and chemicals. The project investigates an alternative approach – “dry” reforming of methane (DRM) - which utilizes captured CO2, rather than steam, to generate CO and H2, thus decreasing the overall GHG inventory. Methane reforming, via any technology, is an energy intensive process. Catalysts are utilized to reduce operating temperatures, improve process efficiency, and drive the reactions to desired products. Dry reforming is even more challenging than steam reforming, thus creating a need for research aimed at identifying more active and selective catalysts that are stable under high-temperature reaction conditions. The project addresses those needs by combining theoretical, computational, and experimental methods to identify effective DRM catalysts. In addition, the project will investigate economics of DRM technology, and incorporate educational and outreach activities exposing high-school and undergraduate students to the field of chemical engineering – so important to the fuels, chemicals, and environmental industries. DRM catalysts must operate at high temperatures, which can destroy carefully designed synthetic structures or promote secondary reactions (e.g., reverse water-gas shift reaction (RWGS) and coke formation) that result in lower value products. One mechanism associated with both the primary and secondary processes is the ability of some catalysts to store and release oxygen during different parts of the cycle. Other catalysts can avoid this oxygen-centric route at the expense of higher activation energies. This work develops hybrid catalysts, using both reducible and non-reducible oxides, to combine the best properties of both in generating highly stable and chemically selective methane reforming catalysts which can be used to operate at industrially relevant conditions. The simultaneous methane reforming and RWGS reactions over ceria catalysts occur through mobile oxygen species. Non-reducible catalyst overlayers have the potential to limit hydrogen spillover from the active metal sites, preventing the unwanted secondary reaction and stabilizing the carefully designed catalyst structure without limiting the role of oxygen in the methane reforming. Using a combination of simulation (density functional theory) and experimental work, the project will develop highly active and structurally stable catalysts while limiting the undesired RWGS, which decreases the H2:CO ratio. However, subsequent reactions to make chemicals require higher H2-to-CO ratios than are possible under standard dry reforming conditions. As such, the optimized hierarchical catalysts will be tested under harsh conditions in the presence of low concentrations of water (i.e., a steam/CO2 “bi-reforming” process) to further increase the H2-to-CO ratio.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

天然气的燃烧（主要由甲烷组成，即CH4）提供了我们国家能源需求的很大一部分。尽管甲烷是一种相对的“清洁”化石燃料，但其组合产生了二氧化碳（CO2），这构成了温室气体（GHG）排放的主要组成部分。甲烷也可以与蒸汽（H2O）反应，以在称为甲烷蒸汽重整的过程中产生一氧化碳（CO）和氢（H2）。产品CO和H2气体进一步反应以产生各种燃料和化学物质。该项目调查了一种替代方法 - 甲烷（DRM）的“干燥”改革 - 它利用捕获的二氧化碳而不是蒸汽生成CO和H2，从而减少了整体温室气体库存。通过任何技术，甲烷改革是一个能源密集型过程。催化剂用于降低工作温度，提高过程效率并推动对所需产品的反应。与蒸汽改革相比，干燥的改革更具挑战，因此，需要进行研究，旨在识别在高温反应条件下稳定的更活跃和选择性的催化剂。该项目通过结合理论，计算和实验方法来识别有效的DRM催化剂来解决这些需求。此外，该项目将调查DRM技术的经济学，并纳入教育和外展活动，使高中生和本科生在化学工程领域中展现出对燃料，化学品和环境行业的重要性。 DRM催化剂必须在高温下运行，该催化剂可以破坏精心设计的合成结构或促进次级反应（例如，反气水电偏移反应（RWGS）和可口可乐形成），从而导致较低的价值产物。与主要和次要过程相关的一种机制是某些催化剂在周期的不同部分中储存和释放氧气的能力。其他催化剂可以避免以较高的激活能为代价。这项工作开发了使用减少和不可还原氧化物的混合催化剂，以结合产生高度稳定和化学选择性的甲烷改革催化剂的最佳特性，这些催化剂可用于在工业相关的条件下运行。甲烷改革和RWG对陶瓷催化剂的反应通过移动氧发生。不可还原的催化剂叠加剂有可能限制活性金属位点的氢晶体，从而防止了不良的次级反应，并稳定了精心设计的催化剂结构，而不会限制氧气在甲烷改革中的作用。使用仿真（密度功能理论）和实验工作的组合，该项目将开发高度活跃和结构稳定的催化剂，同时限制UNESIRE RWG，从而降低了H2：CO比率。但是，随后的使化学物质的反应需要更高的H2-CO比率，而不是理解标准的干燥改革条件。因此，在存在低浓度的水（即蒸汽/二氧化碳“双重改革”过程）的情况下，将在有害条件下测试优化的层次催化剂，以进一步提高H2-to-CO比率。此奖项反映了NSF的立法任务，并以基础的知识优点和广泛的评价来评估，这是NSF的统计任务。