| Summary: | We have carried out a systematic investigation of the critical activation parameters (i.e., final temperature (673–1273 K), atmosphere (He vs. O<sub>2</sub>/He), and final isothermal hold (1 min–15 h) on the generation of “<i>α</i>-sites”, responsible for the direct N<sub>2</sub>O decomposition over Fe-ZSM-5 (Fe content = 1200–2300 ppm). The concentration of <i>α</i>-sites was determined by (ia) transient response of N<sub>2</sub>O and (ib) CO at 523 K, and (ii) temperature programmed desorption (TPD) following nitrous oxide decomposition. Transient response analysis was consistent with decomposition of N<sub>2</sub>O to generate (i) “active” <i>α</i>-oxygen that participates in the low-temperature CO→CO<sub>2</sub> oxidation and (ii) “non-active” oxygen strongly adsorbed that is not released during TPD. For the first time, we were able to quantify the formation of <i>α</i>-sites, which requires a high temperature (>973) treatment of Fe-ZSM-5 in He over a short period of time (<1 h). In contrast, prolonged high temperature treatment (1273 K) and the presence of O<sub>2</sub> in the feed irreversibly reduced the amount of active sites.
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