Performance of Mo modified γ-Fe2O3 catalyst for selective catalytic reduction of NOx with ammonia: Presence of arsenic in flue gas

Effect of Mo on the activity and arsenic resistance ability over gamma-Fe2O3 catalyst for selective catalytic reduction of NOx with NH3 was studied in this work and the anti-arsenic mechanism of Mo-Fe2O3 catalyst was also proposed. Arsenic in flue gas preferred to combine with active iron sites on catalyst, and dramatically consumed surface Lewis and Bronsted acid sites although it provided weak As-OH Bronsted acid sites on poisoned catalyst. The reactions between coordinated ammonia and gaseous NOx on gamma-Fe2O3 were inhibited after arsenic poisoned. With introduction of Mo into gamma-Fe2O3 catalyst, it was found that Mo improved the de-NOx activity under the temperature range of 200-400 degrees C and took great effect on anti-arsenic poisoning for gamma-Fe2O3 catalyst. Interactions between Mo and active iron in catalyst were the key role in preventing active iron from arsenic occupying. And corresponding reactions between adsorbed ammonia and NOx on catalyst were protected.