Influence of Sodium and/or Phosphorus Addition on the Deactivation of Cu-FER Zeolites for SCR of NOx with NH₃

This work investigates the effect of sodium and phosphorus on the DeNOx performances of model Cu-FER SCR catalysts with two copper loadings (2.8 wt% and 6.1 wt%). These inorganic elements, present in the Biodiesel fuels and lubricants, were added by wet-impregnation using two solvents: water or ethanol. Catalysts were evaluated in standard-SCR conditions as well as in NO and NH₃ oxidation, and characterized by means of H₂-TPR and NH₃ adsorption monitored by FT-IR. It was evidenced that catalytic behaviors were highly influenced by the implemented impregnation route with a stronger impact of water as solvent. Whatever the studied catalysts, NH₃ adsorption capacities decreased after addition of sodium and/or phosphorus. Interestingly, sodium and phosphorus acted differently on the poisoning of NH₃ adsorption sites. Na mainly poisoned Brønsted acid sites and favored a back exchange with Cu²⁺ species (especially when Na was added in water), while phosphorus directly interacted with copper species, mainly in exchange position. The deactivation observed at low temperature (250 °C) was preferentially due to the decrease in NH₃ adsorption together with the increase in the copper-phosphorus interaction, especially for copper species in exchange position.