Fuel oxy-combustion is an emergent technology where habitual nitrogen diluent is replaced by high-pressure supercritical CO2 (sCO2), which increases the efficiency of energy conversion. In this study, the chemical kinetics of the reaction C2H6 ↔ CH3 + CH3, important for combustion in sCO2 environment is predicted at 30-1000 atm and 1000-2000 K. We adopt multiscale approach, where reactive complex is treated quantum mechanically in rigid rotor/harmonic oscillator approximation, while environment effects at different densities are taken into account by potential of mean force (PMF), produced with classical molecular dynamics (MD). Here we used boxed MD, where enhanced sampling of infrequent events of barrier crossing is accomplished without application of bias potential. Multi-state empirical valence bond (MS-EVB) model was applied to describe free radical formation accurately at the cost of classical force field. Predicted rates at low densities agree well with the literature data. Rate constants at 300 atm is 2.16×1016 T-0.53 exp(-77.04 kcal/mol/RT) 1/s for ethane dissociation and 4.24×10-13 T-0.0184 exp(14.96 kcal/mol/RT) cm3/molecule/s for methyl-methyl recombination.

Computational kinetics in supercritical CO2 environment: Ethane dissociation and recombination reactions C2H6 ↔ CH3 + CH3

2019 Spring National Meeting

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