Importance of the lifetime of oxygen species generated by N2O decomposition for hydrocarbon activation over Fe-silicalite

Transient isotopic studies in the Temporal Analysis of Products (TAP) reactor evidenced a clear mechanistic regularity between methane and propane for N2O reduction over Fe-silicalite in the temperature range of 623-773 K. The lifetime of the oxygen species generated by N2O decomposition on extraframework iron sites was found to be crucial for alkane oxidation. When N2O and CH4 or C3H8 were Pulsed together over Fe-silicalite, oxygen species deposited on iron sites effectively activated the hydrocarbon. However, these oxygen species become inactive for alkane oxidation if the pulses of N2O and the alkane were separated by more than 0.1 s. Transient studies have indicated that C3H8 is more efficient for N2O reduction than CH4, as expected from the facilitated activation of the C-H bond upon increasing the carbon number in alkanes. The performance derived from the TAP reactor agrees well with experiments under flow conditions at ambient pressure. (c) 2005 Elsevier B.V. All rights reserved.