Enhancement of the catalytic activity of Cu-ZSM-5 for nitric oxide decomposition by introduction of copper during the zeolite synthesis

Decomposition of nitric oxide over different metal containing ZSM-5 catalysts was studied. The catalysts were prepared by ion-exchange, impregnation, metal introduction during synthesis and combinations of these methods. Introduction of copper during synthesis of the ZSM-5 catalyst combined with copper ion-exchange resulted in a catalyst, Cu(i)-Cu(s)-ZSM-5, which was more active than only copper ion-exchanged ZSM-5, Cu(i)-ZSM-5. Catalysts with Co, Ni or Ga introduced during synthesis combined with copper ion-exchange had about the same activity as Cu(i)-ZSM-5. Impregnation of the copper ion-exchanged ZSM-5 catalyst with Cu, Co, Ni or Ag, using the incipient wetness technique decreased the conversion. Temperature-programmed desorption studies of nitric oxide from pre-oxidized catalysts indicated a larger number of active sites for the Cu(i)-Cu(s)-ZSM-5 compared to Cu(i)-ZSM-5.