An ab initio kinetic study on competitive pathways in H-abstraction reactions from γ-valerolactone

γ-Valerolactone (GVL) has been regarded as a promising oxygenated biofuel and fuel additive, as it shows high energy density and can achieve more complete combustion compared to conventional hydrocarbon fuels. However, as a cyclic methyl ester, its unique molecular structure makes the combustion chemistry more complex than that of small linear esters, which remains still not fully understood. In this work, the potential energy surfaces of H-atom abstraction from GVL by H, CH 3 , C 2 H 5 , O, OH, CH 3 O, O 2 , HO 2 , and CH 3 OO were systematically investigated using high-level ab initio calculations, while the temperature-dependent rate coefficients were calculated using conventional transition state theory or RRKM theory over 500–2500 K. For a specific H-abstraction site, the barrier heights follow the order of OH < O ≈ CH 3 O < H < CH 3 ≈ C 2 H 5 < CH 3 OO ≈ HO 2 < O 2 . For a given abstractor, the barrier heights generally increase in the order of C γ < C α < C β < C methyl , identifying the tertiary C γ site as the most reactive abstraction site. OH-initiated abstraction exhibits the highest rate coefficients at low and intermediate temperatures due to its very low barriers, including a submerged barrier for the C γ channel. However, its total rate coefficient shows relatively weak temperature dependence, whereas the reactions initiated by O and H atoms increase more rapidly with temperature. Consequently, the total rate coefficients by O atom and H atom exceed that by OH radical when the temperature increases beyond 1200 K and 1800 K, respectively. H-abstraction reactions by O 2 remain the slowest pathway throughout the investigated temperature range, because of its exceptionally high barriers. These newly calculated rate coefficients are observed to improve the prediction performance of GVL kinetic model in literature, which better reproduces the mole fractions of methane and 1-butene during GVL pyrolysis in a plug flow reactor.