Kinetic modeling study of CO oxidation in the presence of H2 over Pt/Rh/Al2O3 catalysts

Nikola  Rankovic, IFP Energies Nouvelles -Lyon

Kinetic modeling studies of CO oxidation in the presence of H2 over Pt/Rh/Al2O3 catalysts

Nikola Rankovic (a,b), Andr? Nicolle (a), David Berthout (a), Patrick Da Costa (a,b)
(a) IFP Energies Nouvelles, 1-4 avenue de Bois-Pr?au, 92852 Rueil Malmaison Cedex, France
(b) Institut Jean Le Rond d?Alembert ? Universit? Pierre et Marie Curie ? Paris 6, CNRS UMR 7190, 2 place de la gare de ceinture, 78210 Saint-Cyr-l??cole, France

Microkinetic modeling was used to interpret the kinetics of the carbon monoxide oxidation in the hydrogen-rich mixtures over 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 H2 was well described for Pt/Al2O3 and Rh/Al2O3 catalysts using the microkinetic approach. Furthermore, a global Langmuir-Hinshelwood rate expression was developed on the basis of the microkinetic model and successfully implemented in the AMESim modeling platform. Both detailed and global model predict correctly the CO conversion profiles and the enhancement effect of hydrogen to the CO lightoff temperatures in the CO/H2/O2 system. This promoting effect was attributed to the surface reaction between CO(s) and OH(s) that represents an alternative way of consuming CO(s) on the noble metal surface. Two monometallic models were then assembled to simulate CO conversion profiles over a bimetallic Pt/Rh/Al2O3 catalyst. The interactions between platinum and rhodium arising from alloying were described by accounting for the surface enrichment in platinum.

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