Diethyl ether oxidation: Revisiting the kinetics of the intramolecular hydrogen abstraction reactions of its primary and secondary peroxy radicals

Abstract

• Reaction kinetics of intramolecular hydrogen abstraction reactions of peroxy radicals yielded by diethyl ether are revisited with high level ab initio calculations. • The individual role of variational, tunneling and multistructural torsional anharmonicity effect in the calculation of rate constant is analyzed in detail. • The special effects of diastereomers and conformers generated via pseudo-rotations within the saddle point ring are emphasized. • The prediction performances of several representative chemical kinetic models of diethyl ether updated with our calculated rate constants are tested. • 1 Yaozong Duan, M. Monge-Palacios and E. Grajales-Gonzalez contributed equally. Diethyl ether is an attractive alternative to diesel fuel for its high autoignition propensity, high energy density, and potential to reduce pollutant emissions. Low-temperature oxidation kinetics play an important role governing fuel autoignition in engines. Peroxy radical intramolecular hydrogen atom abstraction reactions are key isomerization steps in the chain branching reaction sequence at low temperatures. In this study, the kinetics of intramolecular hydrogen atom abstraction reactions of the primary and secondary peroxy radicals were revisited using the multistructural torsional variational transition state theory with small curvature tunneling corrections. High-pressure limit rate constants within a broad temperature range were obtained, which differ from those previously reported for the investigated reactive systems due to the differences in the estimated barrier heights, the role played by multistructural torsional anharmonicity, and the effects of tunneling. We also observed that some higher energy conformers of the saddle point species, some of which with diastereomers, play a surprisingly large role. Similarly, tunneling is pronounced at low temperature combustion conditions, claiming for robust methods to estimate this effect. Different kinetic models for diethyl ether were used to test our calculated rate constants and NASA polynomials for both diethyl ether peroxy radicals, and the results showed an overall slightly better performance in the prediction of ignition delay times at high pressures.