| NSF Org: |
CBET Division of Chemical, Bioengineering, Environmental, and Transport Systems |
| Recipient: |
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| Initial Amendment Date: | March 29, 2021 |
| Latest Amendment Date: | May 21, 2021 |
| Award Number: | 2116724 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Robert McCabe
CBET Division of Chemical, Bioengineering, Environmental, and Transport Systems ENG Directorate for Engineering |
| Start Date: | April 1, 2021 |
| End Date: | March 31, 2024 (Estimated) |
| Total Intended Award Amount: | $299,966.00 |
| Total Awarded Amount to Date: | $299,966.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
2601 WOLF VILLAGE WAY RALEIGH NC US 27695-0001 (919)515-2444 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
NC US 27695-7905 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | Catalysis |
| Primary Program Source: |
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| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.041 |
ABSTRACT
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.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
This project focused on preparation and characterization of thin film model catalysts in the context of chemical looping - oxidative dehydrogenation (CL-ODH) of ethane to produce ethylene. Ethylene production accounts for over 200 million tons of CO2 emission each year worldwide. This is largely due to the inherent limitations of traditional steam cracking technology. The CL-ODH approach has the potential to be significantly more efficient, and it relies on a redox catalyst which functions both as a catalyst and reactive separation agent for in-situ air separation. Our previous study indicated that MnO based oxides, when promoted with Na2WO4, are highly selective. However, detailed mechanistic understanding is lack given the complexity and inhomogenity of the powder catalysts.
In the current project, we successfully prepared smooth epitaxial MnO (and Mn3O4) films on an MgO (001) substrate. We probed various growth conditions such as temperature and oxygen dosage to establish the optimal condition for MnOx growth, as well as the ability to control its oxidation state. Following that, we investigated different approaches to deposite the sodium tungstate promoter on the thin film. These thin film model catalysts were characterized in detail, which led to important understandings of the stability of the various tungstate phases under varying temperatures in vacuum. They also enabled us to perform further mechanistic studies to understand the underlying reaction mechanism behind the role of sodium tungstate promoter in suppressing COx formation while promoting ethylene yield.
Last Modified: 08/08/2024
Modified by: Fanxing Li
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