(25a) Ab Initio Study on the Methyl Butanoate Decomposition

Methyl butanoate (MB) has been widely used as a convenient surrogate for biodiesel fuels in flame simulation [1-3]; however the kinetics as well as the breakdown mechanism for such a compound have not been verified/explored intensively from a theoretical approach (OR theoretical point of view). In this study, density functional theory (DFT) methods, namely BH&HLYP and B3LYP, have been used to explore the potential energy surface for the identified main pathways of MB breakdown. The RRKM and the Master Equation (ME) methods have been used to derive pressure-dependent rate constants for unimolecular reactions in high-pressure-limit and atmospheric regime, respectively. The canonical transition state theory (TST) is also employed to calculate thermal rate constants for bimolecular reactions. The pattern of the MB decomposition is then served as a prototype for identifying important breakdown pathways and assigning kinetic parameters for such pathways for low molecular weight triglycerides, e.g. tributyrin.