Long term energy, environmental, and economic needs have motivated the study of renewable energy sources to replace fossil fuels. In order to limit the United States’ production of CO2 from motor vehicle transport, the Department of Energy (DOE) developed the “Co-Optima” program to simultaneously optimize the selection of novel biofuels and the design of efficient engines to maximize performance, efficiency, and adoption. To predict the combustion kinetics of a single novel fuel requires the construction of a reaction mechanism consisting of thousands of elementary reactions and their kinetic parameters. The reaction rates can be determined by performing transition state theory (TST) calculations on each elementary reaction. However, with dozens of novel biofuels being considered, and each fuel having its own reaction mechanism, the TST calculations must be automated. We present a fully-automated method to determine reaction rates via Automated Transition State Theory (AutoTST) calculations. We focus here on the abstraction of hydrogen by six common radicals (*H, *CH3, *OH, *OOH, *O, and O2) present in combustion from 23 biofuel candidates. Hydrogen abstraction reactions are one of the primary reaction families that facilitate combustion and is arguably the most important class of reactions in the combustion process; therefore, determining kinetic parameters for these reactions is crucial. To determine kinetic parameters for these abstraction reactions, we utilize our AutoTST method – a tool based off of the framework of the Reaction Mechanism Generator (RMG). AutoTST estimates the transition state geometry using a group contribution and distance geometry method, performs series of partial DFT geometry optimizations to converge on an optimized transition state geometry, implements intrinsic reaction coordinate calculations to verify the transition state, and uses CanTherm (a canonical transition state theory calculator) to determine kinetic parameters. This method has previously been applied to hydrogen abstractions and results have been compared to published values and benchmark calculations. At the time of writing, we have identified 692 hydrogen abstraction reactions and have successfully kinetics parameters for 322 of these reactions.The application of AutoTST is broad and can be applied to all reaction families of combustion reactions given proper resources.

Determining kinetic parameters of hydrogen abstraction from novel biofuel candidates through automated transition state theory calculations

256th National Meeting (2018)

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