Alkali-Resistant Catalytic Reduction of NO_x via Naturally Coupling Active and Poisoning Sites

摘要

Releasing the poisoning effect of alkali metals over catalysts is still an intractable issue for selective catalytic reduction (SCR) of NO_x with ammonia. The presence of K in fly ash always dramatically suppressed catalytic activity by impairing acidity and redox properties, leading to severe reduction of lifetime for SCR catalysts. Herein, alkali-resistant NO_x reduction over TiO_2-supported Fe_2(SO_4)_3 catalysts was originally demonstrated via naturally coupling active and poisoning sites. Notably, TiO_2-supported Fe_2(SO_4)_3 catalysts expressed admirable NO_x conversion and K resistance within a quite broad temperature window of 200-500 °C. The catalysts with more conserved sulfate species revealed that sulfate groups preferred to migrate from the bulk phase to surface, thus effectively binding with K poisons to release the damage on iron active sites. Because of protection effects of migrated sulfates and closely coupling effects with Fe active sites, NH_3 and NO adsorption amounts and rates were well maintained. In this way, Fe metal sites and sulfate species closely coupled together on a self-preserved TiO_2-supported Fe_2(SO_4)_3 catalyst played essential roles as highly active sites and unique poisoning sites. This work paves a new way to design SCR catalysts with superior alkali resistance that are more reliable in practical deNO_x application.