Efficient Fe-ZSM-5 catalyst with wide active temperature window for NH3 selective catalytic reduction of NO: Synergistic effect of isolated Fe3+ and Fe2O3

摘要

The influence of preparation conditions (urea as precipitant, H-2 reduction, and air passivation) on the catalytic performance and mechanism of Fe-ZSM-5 for NH3 selective catalytic reduction of NO was systematically investigated to understand the effect of iron species in depth. An appropriate molar ratio of urea addition to Fe-ZSM-5 prepared in a mixed solvent formed a large amount of Fe2O3, which increased the low-temperature activity. H-2 reduction transformed some Fe2O3 into elemental Fe, which weakened the inhibiting effect of NH3. It showed more than 90% NO conversion at 125 degrees C, but the loss of active components and Bronsted acid sites caused deteriorating high-temperature performance. Air passivation generated some isolated Fe3+ and adsorbed oxygen species on the surface, which resulted in similar low-temperature activity as a hydrogen-reduced catalyst. Moreover, the regenerated Fe2O3 caused more NH4+ to combine with Bronsted acid sites, which maintained excellent high-temperature performance. (C) 2019 Elsevier Inc. All rights reserved.