Oscillating behavior in N2O decomposition over Rh supported on zirconia-based catalysts 2. Analysis of the reaction mechanism

The mechanism responsible for the oscillating behavior in N2O decomposition of rhodium particles supported on zirconia-based oxides in the presence of oxygen and water is studied using transient reactivity and thermogravimetr ic tests. The behavior over different oxide supports is also reported. The results demonstrate that (i) the atomic oxygen produced in the decompositio n of N2O remains chemisorbed on the Rh surface, leading to its progressive accumulation, (ii) the activity of the catalyst increases progressively wit h increasing coverage of Rh with oxygen, and (iii) above a threshold concen tration of oxygen on the Rh surface, a rapid reconstruction of Rh particles occurs with release of the chemisorbed oxygen and the start of a new oscil lation cycle, but only in the presence of water in the feed. It is also sho wn that the presence of water in the feed, inducing the desorption of chemi sorbed oxygen from the Rh surface, stabilizes a more reduced working state of the catalyst surface. (C) 2000 Academic Press.