Potential Energy Surfaces for the Reactions of HO₂ Radical with CH₂O and HO₂ in CO₂ Environment

Abstract

We report on potential energies for the transition state, reactant, and product complexes along the reaction pathways for hydrogen transfer reactions to hydroperoxyl radical from formaldehyde HCO + HO → HCO + HO and another hydroperoxyl radical 2HO → HO + O in the presence of one carbon dioxide molecule. Both covalently bonded intermediates and weak intermolecular complexes are identified and characterized. We found that reactions that involve covalent intermediates have substantially higher activation barriers and are not likely to play a role in hydrogen transfer kinetics. The van der Waals complexation with carbon dioxide does not affect hydrogen transfer from formaldehyde, but it lowers the barrier for hydroperoxyl self-reaction by nearly 3 kcal/mol. This indicates that CO environment is likely to have catalytic effect on HO self-reaction, which needs to be included in kinetic combustion mechanisms in supercritical CO.

Catalytic Effect of Carbon Dioxide on Reaction OH + CO → H + CO2 in Supercritical Environment: Master Equation Study

“…11 The following papers reported van der Waals complexes with CO 2 that lowered the activation barrier for other combustion reactions without changing the mechanism. 12,13 In the latest paper of this series we introduced CBS-QM11 theory level and refined the reaction pathways. 14 In this contribution we return to the reaction, critically important in combustion,…”

Theoretical studies of reaction mechanisms for potential reactions of HNCO with HO2 radicals

“…The subsequent reaction pathway of HO 2 would affect the composition of the troposphere. Therefore, reactions involving HO 2 have been extensively studied with HX (X = F, Cl, Br, I), 12 H 2 CO, 13 XCHO (X = F, Cl), 14 and HCNO. 15 However, to our best knowledge, the reaction of HO 2 and HNCO has never been reported.…”

Molecular Dynamics of Combustion Reactions in Supercritical Carbon Dioxide. 6. Computational Kinetics of Reactions between Hydrogen Atom and Oxygen Molecule H + O2 ⇌ HO + O and H + O2 ⇌ HO2

“…As a part of our efforts to further develop this technology, we have modeled equation-of-state parameters, developed reduced combustion mechanism, and performed counterflow diffusion flame analyses in sCO 2 environment. We also developed the force field to describe water and carbon dioxide in a mixture supercritical state, investigated potential energy surfaces (PESs) of reactions with the existence of CO 2 by density-functional theory (DFT) calculation, − and predicted the rate constant k of several important combustion reactions in high pressure of CO 2 by molecular dynamics (MD) − and DFT simulations. , In this contribution, we report advances in computational methods of reaction rate prediction in supercritical CO 2 and apply these methods to study R1 and R2.…”