Micro-kinetic analysis of direct N2O decomposition over steam-activated Fe-silicalite from transient experiments in the TAP reactor

Mechanistic and kinetic aspects of the direct decomposition of N2O over steam-activated Fe-silicalite were investigated by transient experiments in vacuum (N2O peak pressure of ca. 10 Pa) using the temporal analysis of products (TAP) reactor in the temperature range of 773–848 K. The transient responses of N2O, N2, and O2 obtained upon N2O decomposition were fitted to different micro-kinetic models. Through model discrimination it was concluded that both free iron sites and iron sites with adsorbed mono-atomic oxygen (*single bondO) species are active for N2O decomposition. Oxygen formation occurs via decomposition of bi-atomic (*single bondO2) oxygen species adsorbed over the iron site. This bi-atomic oxygen species originates from another bi-atomic oxygen species (Osingle bond*single bondO), which is initially formed via interaction of N2O with iron site possessing mono-atomic oxygen species (*single bondO). Based on our modeling, the recombination of two mono-atomic oxygen (*single bondO) species or direct O2 formation via reaction of N2O with *single bondO can be excluded as potential reaction pathways yielding gas-phase O2. The simulation results predict that the overall rate of N2O decomposition is controlled by regeneration of free iron sites via a multi-step oxygen formation at least below 700 K.