EAGER: Fe/Mn-Containing Perovskite Oxides Promoted by Alkali Metal Molybdates for Chemical-Looping Catalysis – Thin-Film Preparation and Surface Characterization

天然气是生产广泛用于聚合物材料的化学制造的烯烃的关键原材料。 乙烯和丙烯的生产是化工行业能源密集度最高的工艺之一，每年排放3亿多吨二氧化碳。该项目探索了一种替代目前工业实践的方法，称为化学循环氧化脱氢（CL-ODH）。 与传统ODH相比，CL-ODH具有大幅提高能源效率和降低碳排放的潜力。 该项目的重点是通过在基本层面上了解其工作机制，并利用这种理解来优化催化剂设计，从而提高CL-ODH催化剂材料的性能和耐用性。 该项目的重点是碱金属钼促进的钙钛矿氧化物的机理方面，具体地说，Na 2 MoO 4、Na 2 Mo 2 O 7或K2 MoO 4促进的La0.8Sr0.2FeO3和La0.7Ca0.3MnO3用于乙烷和丙烷的CL-ODH。CL-ODH概念具有极大地加强轻烯烃生产的潜力。研究小组先前发现，钙钛矿氧化物形成了一种核壳结构，其中含Mn/Fe的钙钛矿氧化物核促进了活性晶格氧的储存/交换，而熔融的钙钛矿壳促进了选择性C-H键活化和氧化转化。该项目代表了第一次深入尝试调查这种新型氧化还原催化剂系统的核心，外壳和活性物种的作用。 该项目旨在通过制备薄膜模型催化剂并使用各种表面科学工具进行广泛的表征来揭示CL-ODH反应的潜在机制。 La0.8Sr0.2FeO3和La0.7Ca0.3MnO3的外延生长薄膜将通过聚合物辅助沉积在市售SrTiO 3上制备。随后依次MBE沉积MoO 3和Na/K，并进行O2环境处理。薄膜的生长将在原位监测，并随后表征。 将对具有和不具有碱金属络合物的钙钛矿薄膜样品进行机械研究和反应测试，以建立氧化还原催化剂优化的合理方法。 该项目的结果将由调查人员纳入教学。通过北卡罗来纳州州立大学的凯南奖学金计划，高中教师将参与该项目，以激发学生对STEM职业的兴趣。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

Natural gas is a key raw material for production of olefins used extensively for the chemical manufacture of polymeric materials. Production of ethylene and propylene is among the most energy-intensive processes in the chemical sector, emitting more than 300 million tons of carbon dioxide each year. The project explores an alternative to current industry practice known as chemical-looping oxidative dehydrogenation (CL-ODH). CL-ODH has potential to substantially increase energy efficiency and lower carbon emissions compared to conventional ODH. The project focuses on improving the performance and durability of CL-ODH catalyst materials by understanding – at a fundamental level – the mechanism by which they work, and by using that understanding to optimize catalyst design. The project focuses on the mechanistic aspects of alkali metal molybdate promoted perovskites oxides, specifically, Na2MoO4, Na2Mo2O7 or K2MoO4 promoted La0.8Sr0.2FeO3 and La0.7Ca0.3MnO3 for CL-ODH of ethane and propane. The CL-ODH concept has potential to greatly intensify light-olefin production. The research team has previously discovered that molybdate promoted perovskite oxides form a core-shell structure with the Mn/Fe-containing perovskite oxide core promoting active lattice oxygen storage/exchange, and the molten molybdate shell facilitating selective C-H bond activation and oxidative conversion. This project represents the first in-depth attempt to investigate the roles of the core, shell, and active species for this novel redox catalyst system. The project aims to unveil the underlying mechanisms for the CL-ODH reactions by preparing thin-film model catalysts and performing extensive characterizations using a variety of surface science tools. Epitaxially grown thin films of La0.8Sr0.2FeO3 and La0.7Ca0.3MnO3 will be prepared on commercially available SrTiO3 via polymer-assisted deposition. This is followed with sequential MBE deposition of MoO3 and Na/K, and O2 ambient treatment. The growth of the thin film will be monitored in situ and characterized afterwards. Mechanistic investigations and reactive testing will be performed on perovskite thin film samples both with and without alkali metal molybdates to establish a rational approach for redox catalyst optimization. Results from the project will be integrated in teaching by the investigators. Through the Kenan fellowship program at North Carolina State University, high school teachers will be involved in the project to stimulate students' interest towards STEM careers.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.