On the detrimental effect of tungstates on the n-C10-SCR of NOx on Ag/g-Al2O3
Résumé
The influence of the addition of W to Al2O3,
promoted or not by Ag, on the n-C10 SCR of NOx was
investigated. It was shown that the addition of W was
detrimental to the n-C10 SCR reaction. Based on the NOx-
TPD, the XPS and the n-C10 SCR measurements, it was
concluded that the loss of activity observed at temperatures
lower than 400 C on the Ag/W(5)–Al2O3 catalyst compared
with the Ag/Al2O3 sample is likely due to the preferential
deposition of Ag on the tungstate phase, making it
inactive for the n-C10 SCR reaction which requires the
active silver species to be in close contact with the Al2O3.
At higher temperatures, the occupation, by the tungstates,
of the Al2O3 sites responsible for the n-C10-SCR reaction is
proposed to be an additional drawback accounting for the
detrimental effect of W on Al2O3-supported catalysts
promoted or not by Ag.