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

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.