Alkali and Heavy Metal Copoisoning Resistant Catalytic Reduction of NO 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 with NH. 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 spectroscopy combined with theoretical calculations. The alkali metal K mainly decreased the adsorption of NH on Lewis acid sites and altered the reaction more depending on the formation of the NHNO intermediate, which is highly related to NO adsorption and activation. However, Cd further inhibited the generation of active nitrate intermediates and thus decreased the NO abatement about 60% on potassium-poisoned CeTiO catalysts. Physically mixing with acid additives for CeTiO catalysts could significantly liberate the active Lewis acid sites from the occupation of alkali metals and relieve the high dependence on NO adsorption and activation, thus recovering the NO removal rate to the initial state. This work revealed the copoisoning mechanism of K and Cd on Ce-based de-NO 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.