Effect of Alkali Metal on NH₃‐SCR Performance of Fe–Mn/TiO₂ Catalyst and Its Mechanism

Abstract

The aim of this article is to investigate the effect of alkali metals on the NH₃‐SCR performance of Fe–Mn/TiO₂ catalysts and the poisoning mechanism at 30–170 °C. The catalysts without poisoning, with different kinds of alkali metal poisoning, and with different potassium content poisoning were prepared by impregnation method. The activity tests showed that Na, Ca, and K poisoning could lead to different degrees of catalyst deactivation. Characterization analyses showed that alkali metal poisoning decreases the catalyst specific surface area and pore size, reduces the content of surface–active components Mnⁿ⁺, Feⁿ⁺, and (Oα), and reduces the reduction capacity of Mnⁿ⁺ and Fe³⁺. Mechanism analysis showed that K would reduce the reactivity of Lewis acid sites on the catalyst surface, thus leading to a decrease in the intensity of denitrification reactions conducted via the L–H and E–R mechanisms.