Kinetics of Oxygen Exchange and N 2 O Decomposition Reaction over MeO x /CeO 2 (Me = Fe, Co, Ni) Catalysts.

MeO x /CeO 2 (Me = Fe, Co, Ni) samples were tested in an 18 O 2 temperature-programmed isotope exchange and N 2 O decomposition (deN 2 O). A decrease in the rate of deN 2 O in the presence of oxygen evidences the competitive adsorption of N 2 O and O 2 on the same sites. A study of isotope oxygen exchange revealed dissociative oxygen adsorption with the subsequent formation of surface oxygen species. The same species, more probably, result from N 2 O adsorption and the following N 2 evolution to the gas phase. We supposed the same mechanism of O 2 formation from surface oxygen species in both reactions, including the stages responsible for its mobility. A detailed analysis of the kinetics of isotope exchange has been performed, and the rates of one-atom ( R I ) and two-atom ( R II ) types of exchange were evaluated. The rate of the stage characterizing the mobility of surface oxygen was calculated, supposing the same two-step mechanism was relevant for both types of exchange. The effect of oxygen mobility on the kinetics of deN 2 O was estimated. An analysis of the possible pathways of isotope transfer from MeO x to CeO x showed that direct oxygen exchange on the Me-Ce interface makes a valuable contribution to the rate of this reaction. The principal role of the Me-Ce interface in deN 2 O was confirmed with independent experiments on FeO x /CeO 2 samples with a different iron content.