SO₂-Induced Alkali Resistance of FeVO₄/TiO₂ Catalysts for NO Reduction

Selective catalytic reduction of nitrogen oxides with ammonia (NH₃-SCR) is an efficient NO abatement strategy, but deNO catalysts suffer from serious deactivation due to the coexistence of multiple poisoning substances such as K, SO₂, etc. in the flue gas. It is essential to understand the interaction among various poisons and their effects on NO abatement. Here, we unexpectedly identified the K migration behavior induced by SO₂ over K-poisoned FeVO₄/TiO₂ catalysts, which led to alkali-poisoning buffering and activity recovery. It has been demonstrated that the K would occupy both redox and acidic sites, which severely reduced the reactivity of FeVO₄/TiO₂ catalysts. After the sulfuration of the K-poisoned catalyst, SO₂ preferred to be combined with the surface K₂O, lengthened the K-O_Fe and K-O_V, and thus released the active sites poisoned by K₂O, thereby preserving an increase in the activity. As a result, for the K-poisoned catalyst, the conversion of NO increased from 21 to 97% at 270 °C after the sulfuration process. This work contributes to the understanding of the specific interaction between alkali metals and SO₂ on deNO catalysts and provides a novel strategy for the adaptive use of one poisoning substance to counter another for practical NO reduction.