Mechanistic study of selective catalytic reduction of NO with NH over highly dispersed FeO loaded on Fe-ZSM-5

ZSM-5 supported highly dispersed Fe x O y clusters were prepared by a sol-gel method for selective catalytic reduction (SCR) of NO with NH 3 . XRD, SEM, UV-vis, H 2 -temperature-programmed reduction (H 2 -TPR), NH 3 -temperature-programmed desorption (NH 3 -TPD), and BET analyses all indicated that Fe species mainly existed as highly dispersed surface Fe x O y clusters with a Fe 3+ concentration of 22 wt%. NO-temperature-programmed oxidation (NO-TPO) revealed that the Fe x O y clusters promoted the oxidation of NO to NO 2 , which promoted the low temperature NO X removal. NH 3 was activated above 250 °C and over-oxidation of NH 3 to NO X was not observed, as a result, a NO X removal efficiency of 91% was achieved at 400 °C. Moreover, the SCR reaction route was found to be temperature dependent, below 200 °C, the NO X reduction followed the reaction between NO 2 and non-activated NH 3 . Fast SCR reaction dominated the NO X removal in the temperature window of 200-325 °C. At temperatures above 250 °C, the normal reaction between activated NH 3 and NO compensated the thermodynamic limitation induced suppression of fast SCR. Highly dispersed Fe x O y clusters loaded on Fe-ZSM-5 with a Fe 3+ concentration up to 22 wt% promoted the de-NO X activity with an efficiency of 91%. The reaction route was temperature dependent.