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New research points the way toward better fuel systems

Research by Regents Professor Donald Truhlar and Postdoctorates Prasenjit Seal and Gbenga Oyedepo is helping with the design of biofuel systems that burn more efficiently and effectively. This research was recently published in The Journal of Physical Chemistry and highlighted by the Environmental Molecular Sciences Laboratory (EMSL) of Pacific Northwest National Laboratory.

Burst of Energy: Theory Builds on Experiment, Points Way Toward Better Fuel Systems is available online on the EMSL website, on its news page, and on a specific article page. The complete abstract of this research can be found in The Journal of Physical Chemistry,

New atomic-level details about how butanol burns are making combustion chemistry models more accurate and helping design fuel systems that burn more efficiently and cleanly. Butanol (C4H9OH) is an advantageous alternative to ethanol fuel that can be derived from plants. It stores a great deal of chemical energy in its hydrogen bonds, which are located at five sites—four where hydrogen atoms attach directly to the butanol carbon backbone and one where hydrogen attaches as part of a hydroxyl, or OH, group. With the help of supercomputing resources, including EMSL’s Chinook, researchers studied how these bonds break—releasing a burst of energy—during combustion such as in a vehicle engine. Specifically, they focused on a critical step in the high-temperature combustion process when hydrogen atoms in 1-butanol break away, joining hydroxyl radicals (OH•) to form water. The research team used multistructural variational transition state theory, or MS-VTST, to calculate the reaction rates of this hydrogen abstraction—in other words how readily hydrogen abstraction proceeds—over a range of temperatures for each of the five hydrogen bonding sites. The sum of the five computed reaction rates, or the overall rate, was compared to the overall rate measured experimentally and found to be in excellent agreement. This agreement lends confidence that the five computed reaction rates, which cannot be measured individually using experimental means, are accurate. Adding this fine level of detail about reaction rates to combustion models helps guide chemists and engineers toward fuel systems that maximize energy output and minimize combustion byproducts such as carbon monoxide and soot.

This work was supported in part by the U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences as part of the Combustion Energy Frontier Research Center (CEFRC). Some of the computations were performed at the EMSL, a national scientific user facility sponsored by the DOE's Biological and Environmental Research program.

CEFRC was established by the DOE in August 2009 as one of the 46 centers around the country dedicated to addressing the pressing issues of energy sustainability, energy security, and climate change. CEFRC, funded at $20 million over five years, focuses on the combustion of fossil and alternative fuels to produce heat and power. The research team is led by 15 of the nation’s leading combustion scientists from seven academic institutions and two national laboratories, including Professor Truhlar and researchers at the University of Minnesota.