CAREER: Fundamental Chemistry of Combustion Intermediates: Cyclic Ethers

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The U.S. Energy Information Agency predicts that portion of combustion-derived energy consumed by the transportation sector over the next several decades remains strikingly similar to that in 2020, with hydrocarbons and biofuels providing about ninety-seven per cent. Concurrent with other technologies, continued development of sustainable combustion systems for transportation is a high priority for the United States. Despite numerous advancements over the years, including drastic reductions in emissions and improvements in fuel economy, significant scientific challenges still remain on development of sustainable and low-carbon-intensive energy sources. Improvements in the efficiency of combustion systems is predicated on an understanding of chemical reactions that control ignition and pollutant formation and, moreover, the ability to predict such phenomena via computer modeling. However, fundamental understanding of hydrocarbon and biofuel chemistry becomes more complex in next-generation combustion systems that incorporate new strategies and operating conditions of temperature and pressure that differ from conventional systems. This project specifically focuses on cyclic ethers, which are a class of intermediates formed predominantly at low temperatures as found in modern combustion systems. To contribute to energy efficiency goals for next-generation combustion technologies, this CAREER project tightly integrates research, education, and outreach strategies to produce fundamental knowledge and instructional tools to advance the field of combustion chemistry. This project includes scientific training of Ph.D. students, undergraduate Student Veterans, and first-generation students. The research elements underpin several educational projects, including, among others, combustion science videos produced in collaboration with the Grady School of Journalism, wherein graduate and undergraduate students discuss their research and its broader impact to spur interest in combustion research. The primary research activities of the project involve combustion experiments on cyclic ethers using a high-pressure jet-stirred reactor and the development of new sub-mechanisms using Reaction Mechanism Generator, a leading open-source software for chemical kinetics modeling. The project specifically focuses on cyclic ether radical chemistry, the knowledge gap on the competition of between unimolecular ring-opening and bimolecular reaction with oxygen, and related impact on ignition and emissions predictions. The experiments utilize mass spectrometry and a state-of-the-art electronic absorption spectroscopy technique to measure isomer-resolved species profiles of products from combustion of the six cyclic ethers produced from n-pentane oxidation: 1,2-epoxypentane, 2,3-epoxypentane, 2-ethyloxetane, 2,4-dimethyloxetane, 2-methyltetrahydrofuran, and tetrahydropyran. The scientific impact of this research includes the development of new, fundamental understanding of chemical reactivity relevant to combustion, new cyclic ether sub-mechanisms, as well as improvements to the fidelity of existing chemical kinetics mechanisms, which enable the design and modeling of next-generation combustion systems.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.