Alkali and Heavy Metal Copoisoning Resistant Catalytic Reduction of NO x via Liberating Lewis Acid Sites.

The catalyst deactivation caused by the coexistence of alkali and heavy metals remains an obstacle for selective catalytic reduction of NO _x with NH ₃ . Moreover, the copoisoning mechanism of alkali and heavy metals is still unclear. Herein, the copoisoning mechanism of K and Cd was revealed from the adsorption and variation of reaction intermediates at a molecular level through time-resolved in situ spectroscopy combined with theoretical calculations. The alkali metal K mainly decreased the adsorption of NH ₃ on Lewis acid sites and altered the reaction more depending on the formation of the NH ₄ NO ₃ intermediate, which is highly related to NO _x adsorption and activation. However, Cd further inhibited the generation of active nitrate intermediates and thus decreased the NO _x abatement about 60% on potassium-poisoned CeTiO _x catalysts. Physically mixing with acid additives for CeTiO _x catalysts could significantly liberate the active Lewis acid sites from the occupation of alkali metals and relieve the high dependence on NO _x adsorption and activation, thus recovering the NO _x removal rate to the initial state. This work revealed the copoisoning mechanism of K and Cd on Ce-based de-NO _x catalysts and developed a facile anti-poisoning strategy, which paves a way for the development of durable catalysts among alkali and heavy metal copoisoning resistant catalytic reduction of NO _x .