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

Resolving severe deactivation by alkali metals for selective catalytic reduction of NO with NH (NH-SCR) is challenging. Herein, surface Ce(SO) 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 catalysts, yet commercial VO-WO/TiO catalysts almost lost the NO conversions. Potassium preferably bonded with surface sulfates to form KSO accompanied with the majority of surface Ce(SO) over sulfated CeO catalysts, but preferably coupled with active vanadia to generate inactive KVO species over VO-WO/TiO catalysts. Such an active Ce(SO) species facilitated the adsorption and reactivity of NH and NO, enabling ceria catalysts to maintain high catalytic efficiency in the presence of potassium. Conversely, the introduction of potassium into VO-WO/TiO catalysts caused a considerable loss of surface acidity, hindering catalyst reactivity during the SCR reaction. The self-protection armor of Ce(SO) species may open a promising pathway to develop efficient ceria-based SCR catalysts with strong antipoisoning ability.