Modeling the temperature and pressure dependence of the reaction HO+CO ixHOCO ixH+CO2

Abstract

The bimolecular reaction HO+CO ixH+CO₂ involves the intermediate formation of HOCO. As a consequence, the rate coefficient shows a complicated temperature and pressure dependence. An optimized E- and J-resolved rigid activated complex RRKM theory, with simplified E- and J-resolved pressure-dependent collision efficiencies, fits the available experimental data and allows for extrapolations to unexplored conditions. Experiments between 80 and 2370 K, between 10⁻³ and 10³ bar in the bath gas He, and below 1 bar in Ar, N₂, CF₄ SF₆, and H₂O at 298 K, serve as the database. A limiting low-pressure rate constant for HO removal of k_o=[1.0×10¹³ exp(−8050 K/T)+9.0×10¹¹ exp(−2300 K/T)+1.01×10¹¹ exp (−30 K/T)] cm³ mol⁻¹ s⁻¹ and a limiting high-pressure rate constant of k_∞=[1.23×10¹⁵ exp (−7520 K/T)+1.1×10¹³ exp(−1850 K/T)+8.0×10¹¹ exp(−120 K/T] cm³ mol⁻¹ s⁻¹ will reproduce the results. The pressure dependence of the rate coefficient as a function of the temperature is represented for the bath gases He, Ar, N₂, CF₄, SF₆, and H₂O. Rate coefficients for HOCO formation and HOCO dissociation are also given.