Accurate rate constants for elementary reactions of molecular hydrogen and carbon monoxide mixtures and the role of the H2 rich environment

Abstract

This investigation provides accurate rate constant values for a set of elementary reactions relevant to mixtures between molecular hydrogen (H₂) and carbon monoxide (CO) such as syngas. We considered intermediates and products including formaldehyde (H₂CO), hydroxymethylene (c-HCOH and t-HCOH) and methanol (CH₃OH). The calculations were performed employing the improved canonical variational transition state theory with small-curvature tunneling corrections based on high-level electronic structure results. This study demonstrates for the first time that H₂ can act as an effective catalyst to the reaction from t-HCOH to H₂CO. In this case, the adiabatic barrier height for the reaction decreases from 30.6 kcal⋅mol^{- 1} to 18.1 kcal⋅mol^{- 1} in the presence of H₂. The results obtained here can improve the comprehension regarding processes such as the combustion of hydrogen-rich syngas.

Keywords: Electronic structure; H2-catalysis; Rate constants; Syngas combustion; Transition state theory.