Lean No-x reduction on Cu-NaY and Cu-HZSM5 zeolites at the spark ignition engine exhaust

The lean NOx reduction on the Cu-NaY and Cu-HZSM5 catalysts has been investigated at the spark ignition engine exhaust. Catalysts prepared by exchange method at different Cu loadings were characterized by XRD, XPS, ESR and redox treatments with CO and O-2. The results show similar performances of Cu-HZSM5 and Cu-NaY. Reaction rates, normalized with respect to the total copper, resulted five times higher for Cu-HZSM5 compared to Cu-NaY. The nature of sites active for the lean NOx reduction is compared with that for the NO decomposition. It is concluded that different sites are operated for the two reactions and that a much higher fraction of copper is involved in the lean NOx reduction compared to the NO decomposition.