Kinetic Modeling Study of the Oxidation of Carbon Monoxide-Hydrogen Mixtures over Pt/Al2O3 and Rh/Al2O3 Catalysts

Detailed kinetic modeling was used to interpret the kinetics of the global CO + O-2 reaction in the presence of hydrogen on Pt/Al2O3, Rh/Al2O3, and Pt/Rh/Al2O3 catalysts. The rate parameters were compiled from the literature and optimized to improve the predictivity against multiple experimental data sets. The intrinsic kinetics of CO oxidation in the presence of hydrogen was well described for Pt/Al2O3 and Rh/Al2O3 catalysts. On the basis of microkinetic studies, a global Langmuir-Hinshelwood rate expression for platinum and rhodium was derived. The resulting global rate was successfully implemented in the AMESim modeling platform. Both the detailed and global models predict correctly the CO conversion profiles and the enhancement effect of H-2 to the CO light-off temperatures in the CO/O-2/H-2 system. This promoting effect is attributed to the surface reaction between CO(s) and OH(s) which represents an alternate way for consuming CO(s).