PETR 111 |
| Experiments with isotopic 18O2 were conducted to study the nature of oxygen species participating in the reaction of methane with oxygen to produce H2 and CO during the partial oxidation of methane (POM). Prior experiments, catalysts were "labeled" with 18O. Product distribution as a function of time showed that there was a time delay between the formation of C18O and C16O during the POM over labeled Rh/zirconium-doped ceria (Rh/ZDC) at 700 Celsius and O/C=1. These results led to the conclusion that methane reacts with lattice oxygen. Further confirmation of these results was conducted by Nuclear reaction analysis of labeled Rh/ZDC samples prior and post POM reaction. Concentration profiles of 18O as a function of catalyst depth showed that lattice oxygen was almost completely consumed during the POM reaction. Isotopic exchange reactions between the 18O in the catalyst and 16O in the gas phase as a function of temperature were also conducted over Rh/ZDC and Pt/zirconium-doped ceria (Pt/ZDC). Results showed that the maximum rate of exchange for the former catalyst occurs at lower temperature over Rh/ZDC than over Pt/ZDC, about 200 Celsius. These results were explained by the fact that Rh/ZDC has a significant higher reducibility than Pt/ZDC as evidenced by temperature programmed reduction experiments. Moreover, these results could also explain several reported studies that conclude that Rh-based catalysts have higher catalytic activity than Pt-based catalysts for partial oxidation reactions. Similar experiments to the POM and isotopic exchange reactions will be conducted using Pt& Rh/Alumina and results will allow the comparison of the activity of oxygen ion conducting and non-oxygen ion conducting supports.
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Fuel Processing for Hydrogen Production
1:30 PM-5:20 PM, Tuesday, 12 September 2006 Palace -- Twin Peaks South, Oral
Division of Petroleum Chemistry |