Preparation of Fe-ZSM-5 with enhanced activity and stability for SCR of NOx

Fe-ZSM-5 catalysts are prepared by 320 and 700 °C FeCl3 sublimation into H-ZSM-5 and are characterised by XRD, H2-TPR, NH3-TPD, 27Al MAS NMR, and NO adsorption by DRIFT. Selective catalytic reduction of NO with NH3 and i-C4H10 and NO oxidation to NO2 have been studied. Fe-ZSM-5 prepared by 700 °C FeCl3 sublimation is more active compared with Fe-ZSM-5 prepared by 320 °C FeCl3 sublimation. NO adsorption study by DRIFT shows that FeCl3 sublimation temperature effects the relative distribution of different iron species in Fe-ZSM-5. High temperature FeCl3 sublimation leads to isolated and hydroxylated iron species (–Fe(OH)2) attached to the ion-exchange positions of ZSM-5. Isolated iron species are intrinsically more active in SCR of NO with NH3 and i-C4H10, and NO oxidation to NO2. All Fe-ZSM-5 catalysts deactivate under simulated exhaust gases at 600 °C. Deactivation is due to extensive detachment of iron species from the ion-exchange positions followed by dealumination of zeolite.