Detailed kinetic modeling of dimethoxymethane. Part I: Ab initio thermochemistry and kinetics predictions for key reactions

Despite the great interest in oxygenated methyl ethers as diesel fuel additives and as fuels themselves, the influence of their methylenedioxy group(s) (0-CH2-0) has never been quantified using ab initio methods. In this study we elucidate the kinetics and thermochemistry of dimethoxymethane using high-level ab initio (CCSD(T)/aug-cc-pV(D+T)MB2PLYPD3BJ/6-311++g(d,p)) and statistical mechanics methods. We model torsional modes as hindered rotors which has a large influence on the description of the thermal behavior. Rate constants for hydrogen abstraction by H and CH3 are computed and show that abstraction from the methylenedioxy group is favored over abstraction from the terminal methyl groups. beta-scission and isomerization of the radicals are computed using master equations. The effect of rovibrationally excited radicals from preceding hydrogen abstraction reactions on subsequent hot beta-scission is computed and has large influence on the decomposition of the formed dimethylether radical. The quantification of the effect of the dominant methylenedioxy group using ab initio methods can guide modeling of oxygenated methyl ethers that contain that group several times. (C) 2017 The Combustion institute. Published by Elsevier Inc. All rights reserved.This work was performed as part of the Cluster of Excellence “Tailor-Made Fuels from Biomass” (EXC 236), which is funded by the Excellence Initiative by the German federal and state governments to promote science and research at German universities. We gratefully acknowledge CPU time grant rwth0070 of the RWTH Aachen University Compute Cluster. M.D. is thankful for financial support from the Deutsche Forschungsgemeinschaft (German Research Association) through grant GSC 111.2019-09-0