Efficient NO x Reduction against Alkali Poisoning over a Self-Protection Armor by Fabricating Surface Ce 2 (SO 4 ) 3 Species: Comparison to Commercial Vanadia Catalysts.

Resolving severe deactivation by alkali metals for selective catalytic reduction of NO x with NH 3 (NH 3 -SCR) is challenging. Herein, surface Ce 2 (SO 4 ) 3 species as a self-protection armor originally exhibited antipoisoning of potassium over ceria-based catalysts. The self-protection armor was also effective for other alkali (Na), alkali-earth (Ca), and heavy (Pb) metals, considerably resolving the deactivation of ceria-based SCR catalysts in practical applications. The catalytic activity tests indicated that the presence of ∼0.8 wt % potassium did not deactivate sulfated CeO 2 catalysts, yet commercial V 2 O 5 -WO 3 /TiO 2 catalysts almost lost the NO x conversions. Potassium preferably bonded with surface sulfates to form K 2 SO 4 accompanied with the majority of surface Ce 2 (SO 4 ) 3 over sulfated CeO 2 catalysts, but preferably coupled with active vanadia to generate inactive KVO 3 species over V 2 O 5 -WO 3 /TiO 2 catalysts. Such an active Ce 2 (SO 4 ) 3 species facilitated the adsorption and reactivity of NH 3 and NO x , enabling ceria catalysts to maintain high catalytic efficiency in the presence of potassium. Conversely, the introduction of potassium into V 2 O 5 -WO 3 /TiO 2 catalysts caused a considerable loss of surface acidity, hindering catalyst reactivity during the SCR reaction. The self-protection armor of Ce 2 (SO 4 ) 3 species may open a promising pathway to develop efficient ceria-based SCR catalysts with strong antipoisoning ability.