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

Abstract

We investigated the reaction rates of OH + CO → H + CO in supercritical CO environment with and without additional CO molecule included in reactive complex. Ab initio potential energy surfaces previously reported a lower activation barrier and hence a catalytic effect of additional CO molecule. Here we solve the steady-state unimolecular master equations based on the Rice-Ramsperger-Kassel-Marcus theory (RRKM) and compare the rates for the two mechanisms. We found that the alternative reaction mechanism becomes faster at high pressure and low temperature, when the concentration of prereactive complex with additional CO molecule becomes appreciable. Therefore, this catalytic effect may be important for the chemical processes in CO solvent but is unlikely to play a role during combustion.

Quantum chemical and master equation study of OH + CH2O → H2O + CHO reaction rates in supercritical CO2 environment

“…We found that at higher CO 2 pressures (300 atm) and lower temperatures (below 313 K), the reaction R2 becomes faster than reaction R1, due to the fact that PRCs are present at sufficient concentrations. These findings are consistent with our previous work on autocatalytic effects in the OH + CO → H + CO 2 reaction . The effect of carbon dioxide on OH + CH 2 O reaction would be important in liquid CO 2 at room temperature, but not for oxy‐combustion processes.…”

“…Both C 6 H 6 and PC128 contain six heavy atoms in the planar or nearly planar hexagonal arrangement. This collision model was used to successfully describe pressure dependence on reactive system of a similar size in the past . The buffer gas used was CO 2 in both cases.…”

“…This collision model was used to successfully describe pressure dependence on reactive system of a similar size in the past. 13 The buffer gas used was CO 2 in both cases. The pressure-dependent rate constants were calculated by solving the energy grained, multiple-well master equation for the reactions R1 and R2.…”

“…To obtain a better description of these vdW interactions, we used a higher theory level (CBS‐QM11) and refined the reaction pathways . Next, we applied the master equation solver to obtain rate constants for the OH + CO → H + CO 2 reaction with and without an additional CO 2 molecule …”

“…9,12 Next, we applied the master equation solver to obtain rate constants for the OH + CO → H + CO 2 reaction with and without an additional CO 2 molecule. 13 In this contribution, we investigate the rate of another reaction R1:…”