Deterioration mechanism of selective catalytic oxidation of NH3 to N2 over CeZrO4 by incorporation of alkali metals and calcium

Alkali metals and calcium were added to CeZrO4 mixed oxide by wet impregnation. The CeZrO4 catalyst poisoned by alkali metals and calcium could inhibit the SCO performance. In particular, Na poisoned catalyst showed the lowest NH3 conversion. The structure analysis proved that this poisoning of metal ions could weaken the interaction between cerium and zirconium, particularly K and Na ions. Moreover, the low surface Brønsted acidity might directly reduce the NH3 oxidation performance. The reaction pathway by in situ DRIFTS results at low temperatures (<350 °C) over poisoned catalyst was different from the temperatures above 350 °C, which was followed the -NH and i-SCR mechanism, respectively.