Multistructural torsional anharmonicity and pressure-dependent kinetic studies on methanol/ethanol reaction with amino radical: Implication for combustion modeling

Abstract

The blending of ammonia with alternative fuel alcohols has recently received increasing interest and it has been shown that their cross-reactions significantly influence the ignition process. In the present work, the detailed electronic structure calculations and kinetic studies for the reactions of CH3OH/C2H5OH with NH2 were performed. The rate constants were calculated by Master Equation/Rice–Ramsperger–Kassel–Marcus (ME/RRKM) over a pressure range of 10−1–105 Torr for the pressure-dependent effect caused by reactant complex. The multistructural torsional anharmonicity effects of the reaction were analyzed and the high-pressure limiting rate constants were calculated over a wide temperature range of 250–2000 K by using multistructural variational transition state theory. All calculations considered the tunneling effect. The results show that the CH3OH/NH2 system exhibits pressure-dependent below 550 K, while the pressure-dependent of the C2H5OH/NH2 system can be safely neglected. Besides, the multistructural torsional anharmonicity effect is pronounced for the C2H5OH/NH2 system, especially at intermediate and high temperatures. The channel for the formation of CH2CH2OH is underestimated and the branching ratio of this channel exceeds that of CH3CH2O and CH3CHOH under the multistructural influence at high temperatures. Thus, we updated the kinetic model and further investigation on ignition delay times and sensitivity analysis. The discrepancies in rate constants caused by the kinetic methods mentioned above seems to have a non-negligible effect on the combustion modeling.