Studies on Cu-Containing MFI Zeolites by H_2-TPR and O_2-TPD
SHAN Xuelei, GUAN Naijia , ZENG Xiang, CHEN Jixin, XIANG Shouhe (Institute of New Catalytic Material Science, College of Chemistry, Nankai University, Tianjin 300071, China)
Different metal ion exchanged ZSM 5 zeolites were investigated by means of H 2 temperature programmed reduction (H 2 TPR) and O 2 temperature programmed desorption (O 2 TPD). Pure Cu ZSM 5 and in situ synthesized Cu ZSM 5/cordierite monolithic catalysts were also characterized by H 2 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 O 2 desorption, which indicates that adding Ag and Ce favors the O 2 desorption 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.