Hydrogen formation in propane oxidation on Pt-Rh/CeO2/Al2O3 catalysts
Résumé
Temperature-programmed oxidation (TPO) of propane (200–550°C) was carried out on PtRh/CeO2/ Al2O3 catalysts with oxygen-deficient C3H8/O2 mixtures. On these TPO profiles, two regions of reaction can be observed. ForT<330–350°C propane is oxidized exclusively into carbon dioxide and water. It is at exactly the temperature of complete consumption of oxygen that the formation of hydrogen begins. ForT > 350 ° C, there are two distinct zones in the catalyst bed: total oxidation catalyzed by platinum at the bed inlet and steam reforming catalyzed by rhodium in the outlet zone. Steam reforming is the slow step in the formation of hydrogen. Gas composition (H2, CO, CO2) is always very close to that predicted by the water-gas shift equilibrium, here this reaction being very rapid.