Studies on Cu-containing MFI zeolites by H2-TPR and O2-TPD

Different metal ion-exchanged ZSM-5 zeolites were investigated, by means of H2-temperature-programmed reduction (H2-TPR) and O2-temperature-programmed desorption (O2-TPD). Pure Cu-ZSM-5 and in-situ synthesized Cu-ZSM-5/cordierite monolithic catalysts were also characterized by H2-TPR in order to compare the oxidation states of copper ions on them. The results show that the Cu-ZSM-5 catalyst has superior oxygen storage capacity than the Co-ZSM-5 and Fe-ZSM-5. The catalyst activity for NO decomposition is closely related to this property. Copper ions are the active sites for the reaction. The addition of Ag and Ce as promoters decreases the temperature of O2desorption, which indicates that adding Ag and Ce favors the O2desorption from the catalyst surface. The state of Cu on the Cu-ZSM-5/cordierite monolithic catalyst is different from that on the pure Cu-ZSM-5. Less Cu+species is found on the monolithic sample but it is more stable than that on the pure Cu-ZSM-5.