Microscopic impact mechanism of alkali earth metal poisoning and Ce modification on the deNOx over the ?-Fe2O3 (001) surface

Ce-doped gamma-Fe2O3 catalyst has excellent deNOx and poisoning resistance. However, the NH3-SCR mechanism of improving of Ca poisoning by Ce at atomic level is still unclear. Therefore, the effects of alkali earth metal Ca poisoning on the gamma-Fe2O3 (001) surface and Ce modified Ca-gamma-Fe2O3 (001) surface in the selective catalytic reduction (SCR) of NOx by NH3 were studied. gamma-Fe2O3 catalyst poisoned by Ca results from the decrease of surface acidity and the improvement of stable nitrite/nitrate species. Ce brings extra Lewis acid sites for the NH3 adsorption when it is used to modify the poisoned catalyst, which improves the NH3 adsorption and activation. The adsorption of NO and O2 as well as the decomposition of O2 may be inhibited by the presence of Ce. Most of the stable, inactive nitrite/nitrate species are active and decomposed. The production of NH2 is aided by the enhancement of the dehydrogenation process of NH3. This study provides a direction for prolonging the service life of low-temperature Fe-based deNOx catalysts in industrial cement furnaces.

Automated summary

This study investigates the effects of Ca poisoning on the surface of γ-Fe2O3 catalysts and Ce modified Ca-γ-Fe2O3 catalysts in the NH3 selective catalytic reduction (SCR) of NOx. Ca poisoning leads to a decrease in surface acidity and an increase in stable nitrite/nitrate species. Ce modification provides additional NH3 adsorption sites, improving the adsorption and activation of NH3.