Ab initio-based kinetics of hydrogen atom abstraction from methyl propionate by H and CH3 radicals: a biodiesel model

The kinetics of hydrogen atom abstraction from methyl propionate (MePr), a biodiesel model, by H-center dot and (CH3)-C-center dot radicals, have been studied. Here, we employ density functional theory (BB1K, BMK, M06-2X, M08-HX, and omega B97XD) and ab initio (MP2, CBS-QB3, and G3) calculations. Rate coefficients of each of six-bimolecular reaction pathways of MePr oxidation were calculated using the conventional transition state theory (TST) with Eckart (Eck) tunneling correction over a wide temperature range, 700-1600 K at pressure 1.0 atm. Branching ratios analysis of different reaction channels indicates that abstraction of H atom from C-alpha is the most dominated route for MePr fuel consumption. However, rate constants of H-atom abstraction from the terminal methyl groups increase with rising of temperature for both H-center dot and (CH3)-C-center dot radicals.