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

We investigated the reaction rates of OH + CO → H + CO₂ in supercritical CO₂ environment with and without additional CO₂ molecule included in reactive complex. Ab initio potential energy surfaces previously reported a lower activation barrier and hence a catalytic effect of additional CO₂ 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 CO₂ molecule becomes appreciable. Therefore, this catalytic effect may be important for the chemical processes in CO₂ solvent but is unlikely to play a role during combustion.