Abstract
Fossil fuel oxy-combustion is an emergent technology where habitual nitrogen diluent is replaced by high pressure (supercritical) carbon dioxide. The supercritical state of CO2 increases the efficiency of the energy conversion and the absence of nitrogen from the reaction mixture reduces pollution by NOx. However, the effects of a supercritical environment on elementary reactions kinetics are not well understood at present. We used boxed molecular dynamics simulations at the QM/MM theory level to predict the kinetics of dissociation/recombination reaction HCO• + [M] ↔ H• + CO + [M], an important elementary step in many combustion processes. A wide range of temperatures (400-1600K) and pressures (0.3-1000atm) were studied. Potentials of mean force were plotted and used to predict activation free energies and rate constants. Based on the data obtained, extended Arrhenius equation parameters were fitted and tabulated. The apparent activation energy for the recombination reaction becomes negative above 30atm. As the temperature increased, the pressure effect on the rate constant decreased. While at 400K the pressure increase from 0.3atm to 300atm accelerated the dissociation reaction by a factor of 250, at 1600K the same pressure increase accelerated this reaction by a factor of 100. Graphical abstract Formyl radical surrounded by carbon dioxide molecules.
Published Version
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