Chemical Reaction CO+OH^• → CO₂+H^• Autocatalyzed by Carbon Dioxide: Quantum Chemical Study of the Potential Energy Surfaces

Abstract

The supercritical carbon dioxide medium, used to increase efficiency in oxy combustion fossil energy technology, may drastically alter both rates and mechanisms of chemical reactions. Here we investigate potential energy surface of the second most important combustion reaction with quantum chemistry methods. Two types of effects are reported: formation of the covalent intermediates and formation of van der Waals complexes by spectator CO2 molecule. While spectator molecule alter the activation barrier only slightly, the covalent bonding opens a new reaction pathway. The mechanism includes sequential covalent binding of CO2 to OH radical and CO molecule, hydrogen transfer from oxygen to carbon atoms, and CH bond dissociation. This reduces the activation barrier by 11 kcal/mol at the rate-determining step and is expected to accelerate the reaction rate. The finding of predicted catalytic effect is expected to play an important role not only in combustion but also in a broad array of chemical processes taking place in supercritical CO2 medium. It may open a new venue for controlling reaction rates for chemical manufacturing.

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

“…They calculated activation barrier to be 4.3 kcal/mol. In this work, we will refine that result using higher theory level CBS‐QM11, introduced earlier . Finally, Xu et al .…”

“…[5][6][7][8] In the first paper of this series, we investigated the effect of CO 2 on the CO + OH reactive system and found a lower activation energy pathway in which CO 2 participated covalently. 9 In the following papers, we reported lowering of the activation barrier of seven other combustion reactions via van der Waals (vdW) interactions with CO 2 . 10,11 To obtain a better description of these vdW interactions, we used a higher theory level (CBS-QM11) and refined the reaction pathways.…”

“…Combustion kinetics may alter at large concentrations of CO 2 , and theoretical chemistry can assist in studying these effects . In the first paper of this series, we investigated the effect of CO 2 on the CO + OH reactive system and found a lower activation energy pathway in which CO 2 participated covalently . In the following papers, we reported lowering of the activation barrier of seven other combustion reactions via van der Waals (vdW) interactions with CO 2 .…”

“…In the following papers, we reported lowering of the activation barrier of seven other combustion reactions via van der Waals (vdW) interactions with CO 2 . 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 …”

“…10,11 To obtain a better description of these vdW interactions, we used a higher theory level (CBS-QM11) and refined the reaction pathways. 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:…”