Chemical kinetic study of the low temperature oxidation of Alkanes with a new scheme

Abstract

Leading candidates of advanced internal combustion engine concepts are low temperature compression ignition engines. However, kinetic data for low-temperature oxidation reactions from experimental measurements was limited. Theoretical investigations on kinetic of low-temperature oxidation reactions with high-level quantum chemistry methods are too expensive especially for large fuels. Reliable relative energies can possibly be calculated with proper density functional approximations (DFAs) to obtain reasonable kinetic data for reactions of large fuels. In this work, we investigate performance of nineteen DFAs on reaction energies (REs), barrier heights (BHs) and relative energies of stationary points in seven reaction systems between C2-C4 alkyl radicals and oxygen, which are important low-temperature combustion reactions. Our results show that rDSD-PBEP86-D3(BJ) can provide reliable REs with a mean absolute deviation (MAD) of 0.62 kcal/mol, while different DFAs are suggested for different type of reactions so that MAD on BHs are within 1 kcal/mol. A scheme is proposed where relative energies of stationary points in these reaction systems are determined with rDSD-PBEP86-D3(BJ) for intermediates and final products and with corresponding optimal DFAs for BHs. Pressure-dependent rate constants for reactions in these reaction systems with this scheme are in good agreement with those where relative energies are determined with CCSD(T)-F12a. Moreover, error of relative energies with this scheme is not related to system size. Reasonable kinetic data for low-temperature combustion reaction systems of large hydrocarbon and oxygenated hydrocarbon fuels can be achieved based on relative energies determined with this scheme, which can be used for the construction of low-temperature combustion mechanisms.