Theoretical and Kinetic Study of Hydrogen Abstraction Reactions of Xylene Isomers with Hydrogen and Hydroxy Radicals

Xylenes are important components of gasoline fuels, and their hydrogen abstraction reactions are crucial in the consumption pathways of combustion processes. In existing models, rate constants for these reactions are commonly derived by estimation, which can introduce large uncertainties into models and lead to prediction deviations. In this study, the hydrogen abstraction reactions of three xylene isomers ( p -xylene, m -xylene, and o -xylene) with hydrogen and hydroxyl radicals were investigated using quantum chemical methods. The high-precision CBS-QB3 method was used to perform a series of calculations, including structure optimization, frequency analysis, and energy calculations. Rate constants for all reactions were obtained using transition state theory with tunneling corrections and fitted to the three-parameter Arrhenius expression. The kinetic parameters of these reactions were updated in existing models of xylene. The integration of the updated rate constants into combustion models generally improves predictive accuracy, particularly for ignition delay times, CO 2 formation, and laminar flame speeds, although discrepancies remain for some species such as CO.